天津市大气颗粒物中有机标识物粒径分布的季节特征

Distribution characteristics of organic markers in particulate matter with different sizes during different seasons in Tianjin

为探讨采暖季和非采暖季大气颗粒物中有机标识组分的粒径分布特征,识别其来源,于2018年5月至2019年4月在天津采集分粒径颗粒物,利用GC-MS对9个粒径段颗粒物中17种多环芳烃(PAHs)、20种正构烷烃(n-Alkanes)和7种藿烷(hopanes)进行分析,并通过有机标识物及特征比值的方法探讨其主要来源.结果表明:非采暖季的四环多环芳烃Pyr、BaA、Chr和五环多环芳烃BbF、BaP呈3峰分布,其余PAHs呈双峰分布,采暖季的低环PAHs呈双峰分布,中高环PAHs近似单峰分布.根据PAHs特征比值发现,非采暖季的燃煤源和交通源是PAHs的主要贡献源,采暖季PAHs受燃煤源的影响更显著.非采暖季的正构烷烃中C29呈单峰分布,C27、C31、C32和C33近似单峰分布,其余正构烷烃呈双峰分布,采暖季的正构烷烃均呈双峰分布.根据正构烷烃碳优势指数(CPI)和主碳峰数(Cmax)发现,人为源是正构烷烃的主要来源,非采暖季受自然源的影响大于采暖季,自然源排放的正构烷烃倾向于富集在粗颗粒物上,人为源排放的正构烷烃则更倾向于富集在细颗粒物上.藿烷在粗粒径段和细粒径段均存在峰值.根据藿烷特征比值发现,非采暖季的藿烷受交通源的影响较大,采暖季的藿烷受燃煤源的影响更显著.

In order to study the distribution characteristics of organic markers in particulate matter with different sizes during the heating and non-heating period,and identify their pollution sources,the Anderson eight-stage sampler was used to collect one-year samples from May 2018 to April 2019.17 kinds of polycyclic aromatic hydrocarbons(PAHs),20kinds of n-Alkanes and 7kinds of hopanes in 9particle size segments were analyzed and the main sources of particulate matter were identified by molecular markers and diagnostic ratios.The results showed the 4~5rings PAHs Pyr,BaA,Chr,BbF and BaP showed a three-peak distribution and the rest of the PAHs showed a bimodal distribution during the non-heating period,and 3rings PAHs showed a bimodal distribution and 4~6rings PAHs showed a approximately unimodal distribution during the heating period.The diagnostic ratios of PAHs indicated that vehicle emissions and coal combustion were the main contributors of PAHs during the non-heating period and the coal combustion was the main contributors of PAHs during the heating period.The n-Alkanes showed a stable bimodal size distribution during the heating period and C29 showed a unimodal distribution,C27,C31,C32 and C33 showed approximately a unimodal distribution,with the remaining n-Alkanes in a bimodal distribution during the non-heating period.According to the CPI and Cmax,it is found that anthropogenic sources were the main source of n-Alkanes during the non-heating period and the heating period.The concentration of high molecular weight n-Alkanes was better influenced by natural sources during the non-heating period than during the heating period.In addition,n-Alkanes emitted from natural sources were easy to concentrate in coarser particulates,and n-Alkanes from anthropogenic sources were more likely to concentrate in the finer particles.The hopanes had peaks in both coarse and fine particle modes during two seasons.Traffic was proposed as the main emission source of hopanes during the non-heating period,and the hopanes mainly originated from coal combustion during the heating period.