Study On The Effect Of Meteorological Factors And External Transportation On PM_2.5 In Hengyang City

Due to the comprehensive influence of basin topography and meteorological conditions,the atmospheric pollutants spread slowly in Hengyang City.In order to ascertain the effect of meteorological factors and external transportation on PM_2.5 pollution in Hengyang City,and strengthen the capacity building of air pollution prevention and control with PM_2.5 as the primary pollutant,the correlation between PM_2.5 mass concentration and meteorological factors and the main meteorological factors affecting PM_2.5mass concentration were analyzed in this study,combined with PM_2.5 mass concentration of Hengyang Environmental Monitoring Station and meteorological data of the Hunan Meteorological Center from March 2015 to February 2018.Moreover,backward trajectory pattern of HYSPLIT model was used along with GDAS meteorological data and PM_2.5.5 concentration data of Hengyang to analyze the distribution characteristics of the backward trajectory of the external air mass in Hengyang City.In addition,the distribution of PM_2.5.5 external transport channels and potential sources in Hengyang City were analyzed via cluster analysis method,PSCF method and CWT method.The main conclusions of this study are as follows:?1?Correlation analysis results show that there is a correlation between PM_2.5 mass concentration and meteorological factors such as precipitation,temperature,relative humidity,air pressure and wind speed on the annual time scale:The PM_2.5 mass concentration is positively correlated with the pressure,and negatively correlated with the precipitation,relative humidity,temperature and wind speed.In addition,the PM_2.5 mass concentration in Hengyang City is greatly affected by the northeasterly,easterly and southerly winds throughout the year,but PM_2.5 pollution will increase when the precipitation is in the range of 0 to 1 mm.On the seasonal scale,the concentration of PM_2.5 in Hengyang City is related to different meteorological factors,and there are seasonal differences.?2?The results of multiple linear regression analysis showed that the main meteorological factors affecting the mass concentration of PM_2.5.5 include daily precipitation,daily average temperature,daily maximum temperature,daily average relative humidity,daily maximum wind speed,wind direction of daily maximum wind speed.The wind direction of daily maximum wind speed and daily average temperature has the greatest influence on the PM_2.5mass concentration.?3?The results of backward trajectory distribution show that the seasonal distribution of the external air mass backward trajectory in Hengyang City is obvious.In spring,the external air mass mainly comes from the north direction.In summer,the external air mass is mainly transported in the south direction with a faster speed.In autumn and winter,the air mass transport mainly comes from the northeast direction with a slower speed.In the vertical direction,the external transport path of 100m height is concentrated,and is mainly transported at a short distance.The external transport path of 500m height is more dispersed and the path is longer,and the long-distance transport effect is increased.?4?The results of cluster analysis show that,the air mass transport path from the junction of Hubei and Henan,and then through Hubei and northeastern Hunan to Hengyang is the channel direction of PM_2.5.5 external transport in spring,autumn and winter,with a small contribution rate.In addition,the air mass transport path that passes through the junction of Hunan and Jiangxi and eastern Hunan to Hengyang is the channel direction of PM_2.5with higher contribution rate.In summer,the air mass transport path from the junction of Henan and Anhui,and then through eastern Hubei and northeastern Hunan is the channel direction of PM_2.5.5 external transport.?5?The results of PSCF and CWT analysis show that the regional transportation has a higher contribution rate to the PM_2.5 mass concentration in Hengyang City.With the increase of altitude,the effect of trans-regional transportation increases,and the PM_2.5 mass concentration in winter is most affected by trans-regional transport.The northeastern and southern and eastern parts of Hunan,western Jiangxi,central and southern Hubei,and southern Henan are the main potential source areas for PM_2.5 external transport in Hengyang City in spring,autumn and winter,while the high concentration contribution potential source area of PM_2.5 is in northeastern and southern and eastern parts of Hunan,western Jiangxi.In northeastern Hunan,central and southern Hubei are the main potential source areas for PM_2.5 external transport in summer,and the contribution rate of northeastern Hunan is higher.