Analysis Of The Temporal And Spatial Characteristics Of Tropospheric NO₂ In China And Its Relationship With Socioeconomic Factors

Although the Chinese economy has turned to high-quality development,many environmental pollution problems caused by urbanization and industrialization are still very serious.The burning of fossil fuels and the increase in the number of motor vehicles have led to increasingly serious atmospheric pollution."Twelfth Five-Year Plan"comprehensive work plan for energy conservation and emission reduction included nitrogen oxides as a total air pollutant control indicator for the first time,and specific emission reduction targets were proposed in each of the next five-year plans.As one of the air pollutants,NO₂ is an important precursor of other pollutants.It has a major impact on the climate,ecological environment,and human health.It has severely hindered the development of social economy and the construction of a beautiful China.attention.This article takes the Chinese tropospheric NO₂ column as the research object,using the coefficient of variation,spatial autocorrelation,EKC model,GWR model,GIS technology,geographic detectors and statistics and other related methods,based on the OMI issued by the Royal Netherlands Meteorological Institute Tropospheric Emission Monitoring Network The latest version of the monthly product data of the tropospheric NO₂ column concentration retrieved by the sensor analyzes the temporal change characteristics,spatial distribution characteristics of the tropospheric NO₂ column concentration and the correlation with socio-economic factors.The main conclusions obtained are as follows:1.Temporal variation characteristics of tropospheric NO₂ column concentration（1）Using statistical methods,it is found that the troposphere,the Hu Huanyong line Botai line subarea and the monthly average of the NO₂ column concentration in the six districts from 2010 to 2018 show a"U"-shaped change characteristic,which is similar to the COS cosine function curve,showing obvious winter>autumn>spring>the seasonal characteristics of summer,the annual average change of NO₂ column concentration showed a slight upward trend and then fluctuated downward trend.It reached the maximum in 2011,which was 6.86x1015molec/cm².（2）Using the coefficient of variation method,it is found that the monthly coefficient of variation of NO₂column concentration in the troposphere,the area east and west of the Hu Huanyong line,the area north and south of the Botai line,and the six districts showed a trend of first decline and then increase,and the overall trend was from spring to winter.The upward trend is relatively obvious in Northwest China,and the inter-annual coefficient of variation shows a wave-shaped change trend as a whole.2.Spatial distribution characteristics of tropospheric NO₂ column concentration（1）The monthly,seasonal,and annual average values of tropospheric NO₂ column concentration have obvious spatial regionality.The areas with high NO₂ concentration are mainly distributed in the area with the Beijing-Tianjin-Hebei and Yangtze River Delta as the center,and the Pearl River Delta and the Chengdu-Chongqing Shuangcheng Economic Circle As the central point-shaped area,Urumqi and surrounding areas are sometimes displayed as high-value areas.The NO₂ concentration is higher in the east and lower in the west,and the dividing line is roughly similar to the Hu Huanyong line.The spatial distribution of NO₂ is closely related to the topography and mountain orientation.The high-value areas in the east are mainly surrounded by Changbai Mountain,Xiaoxinganling,Daxinganling,Luliang Mountain,Wushan,Nanling and Wuyi Mountains.The North China Plain has the most serious NO₂ pollution,and the middle and lower reaches of the Yangtze River.The plains are second,and the northeast plains are lighter.（2）East China,Central South and the areas east of the Hu Huanyong line have relatively high NO₂ concentrations in January-February and November-December,while the northwest,southwest,and areas west of the Hu Huanyong line and south of the Botai line are green for almost the whole year.The NO₂ concentration is relatively low.display.In the areas east of East China,Central South and Hu Huanyong Line,the NO₂ concentration in winter is displayed in the red-orange higher value area.The high-value areas of red and orange NO₂ concentration in East China and Central-Southern China from 2010 to 2014 were prominent.The northwest,southwest,west of Hu Huanyong line and south of Botai line had relatively low NO₂ column concentrations during 2010-2018.（3）Using spatial autocorrelation analysis,it is found that the global Moran’s I index for the entire region of China,east of Hu Huanyong Line,north of Botai Line,and south of Botai Line is about 0.80,while the global Moran’s I index of the region west of Hu Huanyong Line is above 0.40,and they are all major Shows HH and LL aggregation patterns.Using trend surface analysis,it was found that the NO₂column concentration showed a trend of high in the east and low in the west in the east-west direction,and showed an"arch-shaped"trend of low on both sides and high in the middle in the north and south.Using the method of center of gravity migration and standard deviation ellipse,it is found that the center of gravity of NO₂ column pollution is constantly changing in Henan and Shandong provinces.The overall migration direction is southwest,and the standard deviation ellipse is mainly distributed in the north-south direction.3.The correlation between tropospheric NO₂ column concentration and socioeconomic factors（1）Use geographic detectors to find per capita GDP（X1）,total population at the end of the year（X2）,cargo turnover（X7）,nitrogen oxides（X10）,urbanization rate（X12）,industrial waste gas treatment investment（X16）,Research and experimental development（R&D）expenditures（X17）and other factors have a greater impact on the spatial differentiation of NO₂,the q value is about 0.5,and the interaction between any two factors is greater than the impact of a single factor on NO₂,showing A non-linear enhancement relationship.（2）Using the EKC model,it is found that there is a negative correlation between the NO2 column concentration and per capita GDP from 2010 to 2018.The factors of the VIF test and Pearson test passed in 2010-2018 are different,and the EKC model obtained is also different.,Reflecting the different correlations between the NO₂column concentration and the influencing factors at different time stages and different economic development levels.Among them,the factors that passed both the VIF test and the Pearson test from 2010 to 2018 were per capita GDP,cargo turnover,and civilian vehicle ownership.Volume and R&D expenditures.（3）Using GWR model analysis,it is found that per capita GDP,cargo turnover,civilian vehicle ownership and R&D expenditures are positively correlated with NO₂column concentration from 2010 to 2018.The regression coefficient of per capita GDP is generally higher in the northeast than in the northwest;the regression coefficient of cargo turnover is similar in space from 2010 to 2015,and the overall performance is gradually increasing from east to west.In 2016-2018,cargo The regression coefficient of turnover volume is similar in space,and the overall performance is higher in the north than in the south;the regression coefficient of civilian car ownership in2010-2018 is higher in the northeast direction and lower in the northwest direction;2010-2018 There is no obvious law in the spatial distribution of the regression coefficients of R&D expenditures.