Polar Organic Compounds In Atmospheric Aerosols Fromthe Farm Of Sichuan Agricultural University In Ya'an

Currently, more attentions are paid to secondary organic aerosols ?SOA? due to their harms on human health, their impacts on global temperature distribution and visibility reduction. In this study, PM_2.5 and TSP samples were collected in Sep.2010, Jan.2011, Apr.2011 and Jun.2011 in the Farm of Sichuan Agricultural University in Ya'an. Samples were extracted with mixed solution, derivatized with N,O-bis-?trimethylsilyl? trifluoroacetamide ?BSTFA? and analyzed by gas chromatography/ mass spectrometry ?GC/MS?. Emphasis was placed on chemical composition, concentration levels and seasonal variation trends of polar organic traces. The results were presented as follows:?1? In PM_2.5 aerosols, the average concentrations of total isoprene oxidation products were 36.4,17.0,37.2 and 50.5ng·m^-3, of ?-/?-pinene oxidation products were 22.8,15.7,8.5 and 21.6ng·m^-3, of ?-caryophyllinic acid were 0.22,0.06,0.02 and 0.04ng·m^-3, of dicarboxylic acids were 183.4,115.6,57.4 and 101.3ng·m^-3, of mono-carboxylic acids were 235.9,346.9,105.7 and 296.2ng·m^-3, of monosaccharide and sugar alcohol were 529.9,542.4,252.5 and 337.5ng·m^-3, and of anhydrosugar were 329.8,143.6,41.8 and 204.8ng·m^-3 in winter, spring, summer and autumn, respectively. In TSP samples, the average concentrations of total isoprene oxidation product were 45.9,15.3 and 47.9ng·m^-3, of ?/?-pinene oxidation products were 14, 15.8 and 15.2ng·m^-3, of ?-caryophyllinic acid 0.12,0.05 and 0.06ng·m^-3, of dicarboxylic acids were 242.5,157.8 and 155.7ng·m^-3, of mono-carboxylic acids were 321.6,340.7 and 186.7ng·m^-3, of monosaccharide and sugar alcohol were 665,735.8 and 441.8ng·m^-3, and of anhydrosugar were 374,154.5 and 108.1ng·m^-3 in winter, spring, and summer respectively.?2? In this study, excellent correlations were observed between 2-methylthreitol and 2-methylerythritol in PM_2.5 and TSP aerosols. C₁₁ mono-carboxylic acids were remarkably correlated with the neighboring odd C₁₃ mono-carboxylic acids. Similarly, C₁₂ mono-carboxylic acids were remarkably correlated with the neighboring even C₁₄ mono-carboxylic acids. However, C₁₆ mono-carboxylic acids and C₁₈ mono-carboxylic acids showed no correlation with each other and with any other mono-carboxylic acids. The mono-carboxylic acids are shown with an obvious even/odd priority:concentrations of even carbon-number mono-carboxylic acids are always higher than those of the neighboring odd carbon-number mono-carboxylic acids.?3? The average concentrations of total isoprene oxidation products in PM_2.5 and TSP aerosols were low in spring and the high in autumn. Levels of a-/(3-pinene oxidation products showed weak seasonal trends during sampling periods. Dicarboxylic acids showed a similar variation trend with mono-carboxylic acids, monosaccharides and sugar alcohols, with the lowest concentrations in summer and peak concentrations in winter and spring.?4? Positive Matrix Factorization ?PMF? was conducted to resolve the sources of polar organic products in atmospheric aerosols. Six factors were obtained with high loading of SOA species. The sources include biomass burning, isoprene and ?-/?-pinene derived SOA, soil dust, agricultural activities, cooking fume and photooxidation process.