二级热脱附结合气相色谱-质谱联用分析大气细颗粒物中多环芳烃类污染物

化学组分是影响大气细颗粒物(即PM_(2.5))健康危害的重要因素,但目前流行病学研究对于颗粒物组分的暴露评价受到了传统分析方法的限制.为探索高效的颗粒物组分测定方法,本研究建立并优化了二级热脱附结合气相色谱-质谱联用(TD-GC-MS)方法,以多环芳烃(PAHs)为目标污染物开展研究.结果表明,该方法具有极高的灵敏度,当使用0.28 m~3PM_(2.5)样品时,该方法的检出限为0.018~0.26 ng·m~(-3).对于标准参考物质的测量显示,该方法具有较好的准确性和精密度.同时,分析了北京2012年3月—2013年3月PM_(2.5)样品并与索氏提取结果进行对比,发现两种方法测量3~5环PAHs的一致性较好;部分物种的差异较大,热脱附因减少前处理步骤,结果可能更为准确.北京PM_(2.5)中∑_(12)PAHs浓度为4.27~340 ng·m~(-3),采暖季比非采暖季高一个数量级.基于正矩阵因子分解法(PMF)的源解析显示,燃煤是采暖季的主要污染源,非采暖季则为交通排放.最后,估算了成年北京居民暴露于PAHs的终生致癌风险,结果表明,可重点控制交通源及煤炭源以降低其潜在危害.

Measurement of polycyclic aromatic hydrocarbons(PAHs) in ambient fine particulate matter using thermal desorption coupled with gas chromatography-mass spectrometry

Chemical composition is a key factor on the health effects of ambient fine particulate matter (i.e., PM_2.5), but so far evaluation of chemical component exposure to PM_2.5 is restricted by traditional analysis approach in epidemiological studies. To explore a highly efficient approach for the analysis of PM_2.5 components, in the present study we developed and optimized a method of two-step thermal desorption coupled with gas chromatography-mass spectrometry (TD-GC-MS) to determine particulate phase polycyclic aromatic hydrocarbons (PAHs). This optimized method was highly sensitive with method detection limits of 0.018 to 0.26 ng·m^-3 when 0.28 m³ PM_2.5 sample was applied. Parallel determination of standard reference materials (SRM, n=5) showed good reproducibility and high accuracy. PAHs levels measured with TD method were compared with those by classic Soxhlet extraction (SE). Good correlations were observed between these two approaches among most 3~5-ring PAHs; TD approach showed higher reliability for several species such as fluoranthene. Concentration of 12 measured PAHs during one-year period in Beijing ranged from 4.27 to 340 ng·m^-3, with much higher concentrations in the heating season than in the non-heating season. A positive matrix factorization (PMF) based source apportionment indicated that coal combustion was the major source during the heating season, while vehicle emission was the predominant one during the non-heating season. Finally we estimated the incremental lifetime cancer risk (ILCR) for adult residents, and it suggested that sources of vehicle emission and coal combustion should be controlled to reduce the risk of PAHs in PM_2.5.