Distribution and sources of solvent extractable organic compounds in PM2:5 during 2007 Chinese Spring Festival in Beijing

The solvent extractable organic compounds (SEOC) including n-alkanes, polycylic aromatic hydrocarbons, fatty acids, and dicarboxylic acids in PM2.5 during the 2007 Chinese Spring Festival in Beijing were measured via gas chromatography to mass spectrometry to determine the characteristics and sources of these organic pollutants. The concentrations of total n-alkanes, PAHs, and organic acids were higher before Chinese Spring Festival Eve (1025.5, 95.9 and 543.3 ng/m3,respectively) than those after (536.6, 58.9, and 331.8 ng/m3, respectively). n-Aalkanes and PAHs had much higher concentration in nighttime than those in daytime because of high relative humidity and low wind speed during the night. Combustion of coal and exhaust emission were major sources of n-alkanes. It could be judged by the characteristic ratios that the primary source of PAHs in fine particles was the combustion of coal, and the combustion of gasoline was in the next place. The ratios of C18:0/C16 indicated the contribution of vehicular emissions to the fatty acids. Dicarboxylic and aromatic acids were abundant in daytime than in nighttime because these acids were secondary organic acid and the photochemical degradation of aromatic hydrocarbons was the main source.