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| Compositions and sources of wintertime dicarboxylic acids in PM10 from Xi￠an |
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Abstract In order to indentify the compositions and sources of organic aerosols in Xi￠an, PM10 samples were collected in the city from January to February, 2009, and characterized for dicarboxylic acids using GC-MS method. Total dicarboxylic acids were [(1597±725) ng/m3] with oxalic acid being the most abundant [(1162±570)ng/m3], followed by phthalic [(196±82)ng/m3], succinic [(98±71)ng/m3] and malonic acids [(58±45)ng/m3]. Dicarboxylic acids in Xi’an were 14%~350% higher than those in other Asian cities. The higher concentrations of diacids in the samples suggested that air pollution in Xi’an was serious and aerosol in the city was more aged. C3/C4, C6/C9 and Ph/C9 ratios indicated that diacids in Xi’an were mostly derived from photo-oxidation of organic precursors emitted from coal burning. Correlations among WSOC, OC, EC and SOC further showed that WSOC in the samples were largely produced by photo-oxidation. Higher temperature and humidity during the sampling period were favorable for the diacids formation, thus, diacids in the samples were still abundant after Spring Festival of 2009 when precursors from coal burning emissions decreased.
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Received: 23 October 2011
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