Analysis of Pollution Characteristics and Potential Sources of Atmospheric Particulate Matter in Qingdao

Based on the atmospheric particulate matter mass concentration of Shandong Qingdao from January 2017 to December 2020， the conventional meteorological observation data and GDAS data， the pollution characteristics of atmospheric particulate matter in this area are studied， and the transmission path of atmospheric particulate matter in Qingdao are analyzed based on HYSPLIT model and TrajStat software.the potential source area and concentration contribution are studied by the Potential Source Contribution Function （PSCF） and Concentration Weighted Trajectory （CWT）.The research findings show： （1） The average annual value of PM2.5 mass concentration in Qingdao was 35.3 µg·m-3.The mass concentration was the highest in winter， followed by spring and autumn， and the lowest in summer.The annual exceeding standard rates of PM2.5 mass concentration were 8.22%， 7.40%， 11.51% and 7.38% respectively.The heavy pollution days only occurred in winter and the pollution days never occurred in summer.（2） The seasonal and diurnal variation of PM2.5 mass concentration presents a "double peak and double Valley" type.The peak value appears at 08:00 （Beijing Time， the same as after） -10:00 and 21:00 -22:00， and the valley value appears at 16:00 -18:00 and 02:00 -04:00.The seasonal diurnal variation of SO2 mass concentration shows a "single peak" type.The daytime concentration is higher than that at night， and the diurnal variation curve fluctuates more obviously in heating season.The diurnal variation of NO2 shows a "double peak and double Valley" type， and the peak time is slightly earlier than that of the diurnal variation of PM2.5.（3） The PM2.5 mass concentration is negatively correlated with air temperature， daily precipitation， wind speed and initial height of inversion， and the correlation coefficients are -0.422， -0.212， -0.106 （wind speed≤2.5 m·s-1） and -0.15 respectively； It is positively correlated with air pressure and inversion intensity， and the correlation coefficients are 0.319 and 0.10 respectively.There is an unobvious correlation between PM2.5 mass concentration and the thickness of atmospheric inversion layer， and the correlation between PM2.5 mass concentration and relative humidity is not unique.（4） The air flow trajectory in spring， autumn and winter comes from the northwest and northerly directions.The northwest air flow accounts for the highest proportion， and they are 70.27%、 75.39% and 100% respectively.The PM2.5 mass concentration in the pollution trajectory is the highest， which is the most important transport path of foreign atmospheric particles in spring， autumn and winter in Qingdao.The southeast air flow trajectory accounts for the largest proportion in summer， accounting for 45.89%.The PM2.5 mass concentration in the pollution track is the highest， which is the main transport path of foreign atmospheric particles in Qingdao in summer.The potential source area of PM2.5 mass concentration has the widest distribution range in winter， the highest WPSCF value， the second in spring and autumn， and the smallest in summer.The main potential pollution source areas and high concentration contribution potential source areas in spring， autumn and winter are located in the south of Hebei， the Middle East of Henan， the west of Anhui， the west of Shanxi and the southwest of Shandong.They are the main source areas for the external transportation of PM2.5 pollution in spring， autumn and winter in Qingdao.The potential source areas of high concentration contribution in summer are located in the southeast of Hebei， the northeast of Henan and the southwest of Shandong and so on.