A Study of Polycyclic Aromatic Hydrocarbons Present in Beijing Aerosols

PM10 and PM2.5 samples were collected in Beijing city during the spring,summer,autumn and winter seasons.Following the U.S.EPA-610 method,18 priority polycyclic aromatic hydrocarbons(PAHs) were quantified by GC-MS.The results show that pollution from inhaled particles(PM10) was serious and that the finer particles(PM2.5) account for much of the pollutant.The PM10 and PM2.5 concentrations are the highest in the spring and decrease in winter,autumn and summer.The concentrations of individual PAHs were 0.10-36.71 ng/m3.The concentrations of PAHs with low molecular weight,such as Nap,Flu or Acy,were very low.The concentrations of PAHs with high molecular weight,such as BghiP,IcdP,B[k]F or BaP,were relatively high;BghiP was the most abundant of the target PAHs.The seasonal variation in the concentrations of the individual PAHs,and of the total PAHs,is: winter autumn spring summer.More than 70% of the PAHs were identified in the PM2.5 samples.The concentration of the PAHs varied with the molecular structure: 5 rings 4 rings 6 rings 3 rings 2 rings.PAHs with four or five rings account for more than 62% of the total PAHs present.Based on the ratios of the PAHs,we conclude that the pollutants mainly come from local sources such as vehicle exhaust and coal combustion and especially from gasoline powered vehicles.