Observational Study Of Black Carbon At Shouxian In Anhui Province

In this paper,the black carbon aerosol concentration data of Shou Xian national climate observatory from November 2015 to November 2018 were used to analyze the temporal variation characteristics of the black carbon aerosol concentration and the impact of meteorological factors on it.In addition,the vertical structure of black carbon in two heavy pollution processes from December 18,2016 to December 19,2016 and January 1,2017 to January 2,2017 was analyzed.The HYSPLIT backward trajectory model was used to assist in determining the direction of the upper air flow,and the vertical structure of black carbon aerosol in the boundary layer was discussed.The main conclusions are as follows:1)from November 2015 to November 2018,the black carbon aerosol concentration in Shou Xian county,An Hui province decreased year by year,which was 2.84,2.10 and 1.31μg·m^-3·m^-1,respectively,with a multi-year average of 2.11μg·m^-3·m^-1.The concentration of black carbon aerosol was high in winter and low in summer,with the concentration of 3.95μg·m^-3·m^-1 in winter,which was about 2.9 times of that in summer. Compared with urban areas,the variation of black carbon aerosol concentration in Shou Xian county showed no significant weekend effect.2)Wind speed and direction have a great influence on the change of black carbon aerosol concentration,and its concentration tends to decrease with the increase of wind speed, while the high concentration value mainly appears in the northwest wind condition.3)The backward track shows the source of air mass in different directions.In the first heavy pollution process,the backward track length at the height of 100m,300m,500m and 700m is short,the wind speed in shouxian area is low,and the advection transport capacity is weak.In the second heavy pollution process,the backward track length is longer at 300 meters and 500 meters,and the wind speed is higher at these two heights,so the advection transportation from the south of Shou Xian county plays a cleaning role.4)Flow transport affects the vertical structure of black carbon in the boundary layer to some extent.When pollution occurs,the near ground is often in a stable stratification,the vertical atmospheric diffusion capacity is not strong.In the middle and upper air,there is strong advection transport in the self-cleaning area,so the concentration of black carbon in the high and low air is obviously stratified,and the concentration of black carbon in the lower 200 meters is greater than 10μg·m^-3,200m-1000m and the concentration in the upper 200 meters is less than 1μg·m^-3.On the contrary,there is no obvious stratification.In this case,as the mixing layer increases,the concentration of black carbon in the atmosphere does not decrease significantly.