Study On The Characteristics Of PM_2.5 Pollution And Its Transportation Path In Typical Cities Of Anhui Province

In recent years,frequent occurrences of ash pollution in areas such as the Yangtze River Delta,the Pearl River Delta,and the Beijing-Tianjin-Hebei region have occurred,fine particulate pollution(PM_2.5)has became the chief culprit in the decline in visibility and the increase in weather in the region.Because of its size≦2.5μm,it can stay in the air for a long time,cause lung cancer,respiratory tract,cardiovascular disease,It even leads to an increase in mortality and a deterioration in meteorological conditions,therefore,it always threatens human health and its living environment.Anhui is located in the Yangtze River Delta,the accelerating urbanization and industrialization process in recent years has made PM_2.5.5 pollution increasingly serious,Although domestic and foreign scholars have carried out a large number of analysis and research on the pollution characteristics and potential sources of PM_2.5,the long-term continuous PM_2.5.5 observation research and analysis in Anhui is still very rare.This paper takes the typical cities of Anhui Province（Bengbu City、Hefei City、Chizhou City）as the research object,based on PM_2.5.5 and meteorological observation data from 2015to 2017,analyzed the temporal and spatial distribution of the mass concentration and the pollution characteristics,studied the effects of other gaseous pollutants and meteorological elements on the mass concentration of PM_2.5,using the backward trajectory mode of Hybrid Single Particle Lagrangian Integrated Trajectory（HYSPLIT）,analyzed the the characteristics of PM_2.5.5 transport path and potential source area in typical cities in winter.The main findings are as follows:（1）In the past three years,the average PM_2.5.5 concentration in Bengbu and Hefei showed a downward trend,while that in Chizhou showed an upward trend.PM_2.5concentration showed seasonal variation pattern of low in summer and high in winter.The monthly change shows a U-shaped curve and the diurnal change shows a W-shaped curve,Hefei City and Bengbu City are characterized by"significant daytime change and gentle night change",while Chizhou City is on the contrary.The spatial variation characteristics of PM_2.5.5 concentration are as follows:Hefei City and Hefei City gradually increase from south to north,the spatial difference between Chizhou City is not obvious.The difference of heavy pollution process between winter and summer was significant,and the concentration of PM_2.5.5 was elevated to a certain extent.（2）There was a significant positive correlation between PM_2.5.5 and PM₁₀,SO₂ and NO₂ were negatively correlated with PM_2.5,and the correlation between autumn and winter was higher than that in spring and summer,the correlation between O₃ and PM_2.5was unstable.PM_2.5.5 is not significantly correlated with temperature and air pressure,but negatively correlated with relative humidity,precipitation and wind speed,and the specific wind direction has a more significant effect on the PM_2.5.5 concentration change.（3）The PM_2.5.5 transportation routes of the three cities are basically in the west and north directions,the main transport route of pollutants in winter in Hefei and Chizhou is short distance,while Bengbu is long distance.In recent three years,the area change of potential sources of pollution in winter shows that the area of Hefei city decreases year by year and gradually concentrates,while Bengbu city has the smallest area,however,the area of the high value area tends to increase.Generally,Chizhou City is similar to Hefei City,but its pollution source area is large and extends far.In the case of heavy pollution in winter,the main transport routes of the three cities under heavy pollution in winter all come from Anhui Province.The primary short-distance transport path of pollutants is shown:Hefei is mainly in the north;Bengbu is mainly in the east to the west;Chizhou is mainly in the northeast.