Particulate Polycyclic Aromatic Hydrocarbons And The Influence Of Meteorological Parameters In Nanjing, China

It was studied that the particulate PAHs concentrations, variations, size distributions and related factors in Nov.2009and Jan.2010, coupled with the corresponding synoptic weather system. And the long-distance transportation of emissions from residue combustion in northern Jiangsu Province was analyzed by the MODIS data and HYSPLIT back trajectory model as well.It showed that there were no significant differences between the two sampling sites on PAHs concentration level, profile and diagnostic ratios, which were testimonies of interaction of atmospheric pollutants in urban and suburban areas by transportation, although they had different local source types separately. Thus one value could depict the items of urban and adjacent suburban areas.But large variation could be found between autumn and winter in urban and suburban Nanjing. The concentrations of particles and particulate PAHs surged to670.67μg·m-3(PM10) and375.63ng·m-3(PM10) respectively, due to the transport of crop combustion emissions and the subsequent haze corruption, while they were similar in other periods.The transported emissions of crop residue combustion could be witnessed by FIRMS fire points, MODIS AOD maps and the isomer ratios analysis, which showed the biomass combustion characteristic. But a mixture of combustion of biomass burning, coal combustion and vehicular emissions showed in winter. The vehicular and industrial emissions, consequently, were always the noticeable emissions in the whole sampling periods in Nanjing.It retained two mode peaks in0.65～1.1μm and4.7～5.8μm respectively in haze episode in autumn. The PAHs size concentration increased dramatically in haze period, which showed a maximum value with4.17folds in fine mode. But the size concentration peaks in coarse mode remained higher than in fine mode and higher in nighttime than in daytime. In haze period, the ratio of PAHs in fine particles to that in the whole size range varies in0.36-0.54, that showed higher ratios for PAHs in coarse mode than in previous studies.There is a part of66%for PAHs sorbed in PM2.1in winter. For2-3ring PAHs, the fine mode is lower than coarse mode, and the opposite for4-6ring PAHs. The synoptic system affected the transport of fine particles significantly. the PAHs concentration correlated with the wind speed non-linearly and did not necessarily decrease with a stronger wind, dependent on the source geographical position. Little correlation was found between PAHs concentration and temperature or humidity. And strong collinearity existed between temperature, humidity and boundary layer variation. Among all the variables, PAHs bulk concentration was influenced more by the source position, wind direction and speed, and aerosol carbon content.