Research On The Correlation Between The Temporal And Spatial Changes Of Atmospheric PM_2.5 And PM₁₀ And Vegetation Coverage In The Urban Area Of ??Xi'an

In recent years,urban airborne particulate pollution has become more and more serious,especially the pollution problems of PM_2.5 and PM₁₀,which seriously affect the health of human beings and cause widespread public concern.This paper takes the main city area of Xi'an,the area north of the Nanheng line,the south of the Weihe River and the area around the east-west expressway as the main research area.The spatial variation of PM_2.5 and PM₁₀ and their relations with vegetation coverage type and vegetation fraction are carried out.Firstly,the time-space distribution characteristics of PM_2.5 and PM₁₀ in the study area were discussed by using the concentration data of PM_2.5 and PM₁₀ automatically sampled by 13 national air quality monitoring stations in Xi'an from 2013 to 2015 and statistical analysis.Secondly,using ENVI and ArcGIS 10.2 software estimated the vegetation fraction?VFC?based on the binarization of the pixel model,and the change of land use type in the study area is comprehensively analyzed.Finally,the SPSS 22 software was used to analyze the correlation between the concentration of particulate matter PM_2.5 and PM₁₀ and the vegetation coverage type and vegetation fraction in the study area.The results show that:?1?According to the change trend of air quality index and the general variation of mass concentration of particulate matter(PM_2.5,PM₁₀)in Xi'an in the past five years can be seen that the temporal variation of air quality index in winter and summer in Xi'an affected by weather conditions is obviously.Increase or decrease in volatility as weather conditions change.The mass concentration of particulate matter(PM_2.5,PM₁₀)in Xi'an is generally high in winter and low in summer,And overall,there is a downward trend.?2?According to the change of vegetation coverage level,the change of vegetation coverage level in Xi'an is mainly from medium-high coverage to low and very low coverage.Some areas is from high coverage to medium and medium-low coverage transform.The change in low vegetation coverage is mainly due to the land use types changes at main built-up areas of Xi'an.In addition to the increase of high coverage area,the whole frame of vegetation cover also change in the study area.The vegetation coverage area changed areas are concentrated in Baqiao District,Weiyang District,Yanta District and Chang'an District,and the most changed type is the type of cultivated land.?3?In the study area,with 11 effective monitoring sites as the center,0.5 km,2 km,and 4 km are used as buffers respectively.Under the buffer scale,from the relationship between vegetation cover types and PM_2.5 and PM₁₀.The average annual mass concentration of PM_2.5 and PM₁₀ is related to the coverage area of vegetation cover type,but the correlation is not significant.In addition,the concentration of PM_2.5 was significantly negatively correlated with the forest area of the buffer area with a radius of 2 km,and the correlation coefficient was-0.809.From the relationship between vegetation coverage and annual average mass concentration of PM_2.5 and PM₁₀,The mass concentration of PM_2.5 and PM₁₀ was negatively correlated with the vegetation coverage of the buffer zone,and the correlation between the two increased from 2013 to 2015.In this study,Kriging interpolation was used to obtain a larger,more accurate,and faster particle concentration data outside the monitoring site.A regression model of PM_2.5 concentration and vegetation coverage was constructed by using SPSS 22 software.From the research results,it is very important to study the effect of forest area on the neighborhood weighted regulation of PM_2.5.The conclusion of this study provides a reference for the study of particulate matter pollution in Xi'an,and provides an important scientific basis for air pollution control and environmental protection in Xi'an.