Characteristics Of Size Distribution And Source Apportionment Of Polycyclic Aromatic Hydrocarbons In Atmospheric Particles During Autumn And Winter In Nanjing,China

In order to understand the characteristics of distribution and source apportionment of polycyclic aromatic hydrocarbons in atmospheric particles during autumn and winter in Nanjing, PM10samples were collected from Nov.20to Dec.30,2007and Nov.l to Nov.14,2009in northern suburbs and urban area of Nanjing by FA-3sampler, the pretreatment was used U.S. EPA To-13method and sixteen PAHs were measured both at day and night using GC-MS. The characteristics of distribution of PAHs were analyzed with meteorological data, HYSPLIT, fire location data and boundary data. The concentration and size distribution of PAHs were also analyzed during a heavy haze episode. PCA was used to analyze the source apportionment of PAHs in particles.The result shows the heavy haze episode was influenced by agriculture burning occurred in Nanjing from Nov.7to Nov.8,2009, the appearance of inversion layer contribute to the haze episode and persistent rain had a strong scavenging ability for pollutants; the concentrations of the particles were as high as579.55and573.43μg·m-3during the haze episode at the city and suburban sites, respectively,3-4times higher than those on a normal day, the proportion of fine particles in the haze episode was also higher than those on a normal day. Changes of concentration of PAHs were in accordance with the concentration of the particles. High-molecular-weight PAHs made up approximately80%of the total PAHs on normal days as well as during the haze episode. There were two peaks at size diameters of0.43-0.65and4.7-5.8μm at both sites in all sampling periods and the concentration of PAHs in fine fraction significantly increased during the haze episode, and it was most obvious at night at the city site. The proportion of total carcinogenic PAHs in fine particles was relatively higher during the haze episode at both sampling sites especially at night in the city. The diagnostic ratio results also indicated that the main sources of PAHs during the haze episode were from coal and biomass burning, but the ratios before and after the haze period were similar.There was no difference between day and night of the concentration of PAHs in atmospheric particles in winter of Nanjing, the concentration of individual PAHs have a large difference between day and night, the concentration of LMW PAHs are higher at daytime, and HMW PAHs are higher at nighttime; the result of PCA show that the main sources of PAHs are vehicles, coal combustion, pyrogenation, natural gas and coking during winter in northern suburbs of Nanjing, and there are differences between PAHs in coarse and fine particles, the sources of PAHs in fine particles have differences between day and night, the uncertain sources and external sources take large part of the total sources of PAHs.