北京市西北城区大气可吸入颗粒物中饱和烃的分布特征

Distribution of saturated hydrocarbons in airborne inhalable particulates of northwestern urban district in Beijing

利用气相色谱、气相色谱 -质谱分析法从北京市西北城区四个季节大气可吸入颗粒物 (PM10 )中检测出种类丰富的饱和烃 ,主要包括正构烷烃、萜烷及甾烷等系列化合物。利用饱和烃的多项参数 (如主峰碳数、碳优势指数CPI、藿烷 2 2S/(2 2S +2 2R)比值等 )对大气PM10 中可溶有机物的来源及分布作了探讨。北京市西北城区PM10 中正构烷烃的主峰碳数均介于 2 3和 2 7之间 ,而CPI值介于 1和 3之间 ,表明北京市西北城区PM10 中的饱和烃均不同程度地受到了高等植物等现代生物和化石燃料 (石油、煤等 )不完全燃烧产物两种来源的影响 ,其中在春、夏季以高等植物、花粉、微生物等生物来源占比重较大 ,而在秋、冬季 ,尤其在冬季 ,化石燃料的不完全燃烧造成的污染比较明显。萜烷类物质的检出 ,表明北京市西北城区四个季节PM10 中部分饱和烃来自于石油等化石燃料的不完全燃烧。甾烷类物质的检出 ,表明北京市西北城区四个季节PM10 中部分饱和烃是来自于车辆释放的机油等。

A series of saturated hydrocarbons,including n-alkanes,terpanes and steranes,have been identified in inhalable particulates (PM 10) samples collected in northwestern urban district in Beijing by means of the GC and GCMS. The parameters of the saturated hydrocarbons,such as major peak carbon number,carbon preference index (CPI) and hopane 22S/(22S+22R) ratios,have been calculated,which can be used to reflect the sources of the extractable organic matters in PM 10. The n-alkanes in PM 10 samples from Beijing air have the major peak carbon numbers ranging from 23 to 27 and the CPI values between 1 and 3,suggesting that the saturated hydrocarbons may be derived from both modern higher plants and incomplete combustion of fossil fuels (coal and petroleum ). The results also show that the saturated hydrocarbons in the spring and summer PM 10 samples are mainly from biomass such as higher plants,pollen and microbes,while the saturated hydrocarbons in the autumn and winter PM 10 samples are mainly from incomplete combustion of fossil fuels. Many terpanes presented in PM 10 similarly indicate a source of incomplete combustion of fossil fuels such as petroleum. Steranes detected in PM 10 imply that parts of saturated hydrocarbons may come from engine oil released by vehicles.