西安市大气中二元羧酸有机气溶胶组成及来源

Compositions and sources of wintertime dicarboxylic acids in PM_(10) from Xi'an

为研究西安市冬季大气PM10中二元羧酸类有机气溶胶的组成和来源,采集了西安市2009年1~2月份的PM10样品,并利用GC/MS对样品中二元羧酸进行了化学表征.结果表明：西安市冬季大气中二元羧酸总浓度为（1597±725）ng/m3,其中草酸浓度最高[（1162±570）ng/m3],其次是邻苯二甲酸[（196±82）ng/m3]、丁二酸[（98±71）ng/m3]和丙二酸[（58±45）ng/m3].西安市二元羧酸浓度高于北京、南京、广州、香港等城市14%~350%,表明其污染严重,其中草酸相对含量远高于国内其他城市,显示西安市冬季大气气溶胶更为老化.C3/C4,C6/C9和Ph/C9比值及其相关性进一步表明二元羧酸主要来自光化学氧化.通过对水溶性有机碳（WSOC）,有机碳（OC）,元素碳（EC）,二次有机碳（SOC）的分析,发现WSOC主要来自于二次有机碳（SOC）的形成.另外,温度升高,相对湿度增加,导致春节后尽管燃煤排放污染物减少,但二元羧酸浓度并无降低,而相对含量较节前却显著增加.

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.