北京市西三环地区大气颗粒物中多环芳烃的分布特性

于2012年3—12月在北京市西三环地区按粒径分6级采集大气颗粒物样品,采用气相色谱-质谱(GC-MS)对颗粒物样品中16种优控PAHs(多环芳烃)进行分析. 结果表明:颗粒物中ρ(∑₁₆PAHs)(PAHs的总质量浓度)季节变化显著,表现为冬季>春季>秋季>夏季,并且与ρ(PM)(PM为颗粒物)呈良好线性相关；不同粒径颗粒物中ρ(PAHs)呈向小粒子富集的趋势,PM_2.1中ρ(PAHs)约占ρ_sum(∑₁₆PAHs)〔6级颗粒物中ρ(∑₁₆PAHs)总和〕的64%~87%；除夏季3环PAHs占优势外,其他季节均以4~ 5环PAHs占优势；同时,随着粒径的减小,PAHs有向高环数富集的趋势. 运用主成分分析和多元线性回归法进行源解析发现,机动车尾气排放和燃煤是本地区大气颗粒物中PAHs的主要来源；不同粒径颗粒物中的PAHs来源有差异,2.1~10.2μm粒径段颗粒物中PAHs主要来源于机动车尾气排放,贡献率为63.0%；而1.3~2.1μm和<1.3μm的颗粒物中PAHs均主要来源于燃煤,贡献率分别为56.8%和58.7%. 

Distribution Characteristics of Polycyclic Aromatic Hydrocarbons in Atomspheric Particulates in the Area of the 3rd West Ring Road in Beijing City

The airborne particles were collected in size grading at the 3rd west ring road in Beijing City from March to December in 2012. The 16priority PAHs in the samples were determined by GC-MS. The seasonal variation with concentrations of the total PAHs was observed. The results showed that the highest value of ρ(∑₁₆PAHs) appeared in winter, followed by the order of spring>autumn>summer. Meanwhile, there were a linear dependence between ρ(∑₁₆PAHs) and ρ(PM). The PAHs were inclined to concentrate in the finer particles, the values of ρ_2.1(∑₁₆PAHs)/ρ_sum(∑₁₆PAHs) accounted for 64%-87%. In general, 4-ring and 5-ring PAHs were the main components in the seasons except summer. The finer the particles were, the higher-ring PAHs were. Principal component analysis and multiple linear regression (PCA/MLR) were applied to identify the source of PAHs in particles. The results showed that PAHs in airborne particulates mainly came from the emission of vehicle engines and coal combustion, and their contributions varied with the particles sizes. The vehicle exhaust mainly contributed to 2.1-10.2μm particles, and coal combustion was the main source of PAHs for the particles of 1.3-2.1μm or smaller than 1.3μm. The contribution rates were 63.0%, 56.8% and 58.7%, respectively.