为了解长三角典型县级市—--义乌市大气 PM$_{2.5}$中烷烃的污染特征和来源, 于 2015 年 7月—2016 年 4 月, 使用 TH-16A 四通道采样器分别在义乌市北苑站点和江东站点采集大气 PM$_{2.5}$样品, 采用气相色谱-质谱联用仪对正构烷烃(C$_{16}\sim $C$_{34})$和藿烷(C$_{27}\sim $C$_{32})$进行定量分析. 结果表明, 北苑站点和江东站点大气PM$_{2.5}$中正构烷烃的年均浓度分别为 78.0 和 80.4 ng/m$^{3}$, 站点之间没有明显差异; 正构烷烃的浓度存在明显的冬季$>$秋季$>$春季$>$夏季的季节性变化规律. 正构烷烃的分布特征、主峰碳数(C$_{\max})$、碳优势指数(carbon preference index, CPI)和植物蜡贡献率(Wax${\%}$)都 表明化石燃料源是义乌市 PM$_{2.5}$中正构烷烃的主要来源, 植物蜡的平均贡献率约为 20${\%}$. 义乌市 PM$_{2.5}$中藿烷的年均浓度在北苑站点和江东站点分别为 5.5 和 4.6 ng/m$^{3}$, 藿烷浓度和正构烷烃浓度之间存在较强的正相关关系. 依据藿烷同系物的分布特征, 机动车排放是义乌市 PM$_{2.5}$中有机质的重要来源.

To understand chemical characteristics and sources of $n$-alkanes and hopanes in the atmospheric PM$_{2.5}$ in Yiwu City, a representative county-level city in the Yangtze River Delta region, seasonal atmospheric PM$_{2.5}$ samples were collected smultaneously at two sites in Yiwu City, Beiyuan and Jiangdong, from July 2015 to April 2016 using TH-16A four-channel samplers. Concentrations of $n$-alkanes (C$_{16}\sim $C$_{34})$ and hopanes (C$_{27}\sim $C$_{32})$ in the PM$_{2.5}$ samples were quantified with gas chromato graphy-mass spectrometer (GC-MS). The results show that the annual average concentration of $n$-alkanes in PM$_{2.5}$ at Beiyuan and Jiangdong were 78.0 and 80.4 ng/m$^{3}$, respectively. No statistical difference in concentration of $n$-alkanes was found between the two sampling sites. A distinct seasonal trend of winter$\to $autumn$\to $spring$\to $summer was found for $n$-alkanes in Yiwu City. The distribution patterns, carbon number maxima (C$_{\max})$, carbon preference index (CPI) and plant wax contribution (Wax${\%}$) of $n$-alkanes all indicated that emissions from fossil-fuel usage was the main source of $n$-alkanes in PM$_{2.5}$ in Yiwu City, while the average contribution of plant wax was about 20${\%}$. The annual average concentration of hopanes in PM$_{2.5}$ at Beiyuan and Jiangdong were 5.5 and 4.6 ng/m$^{3}$, respectively. Strong correlation between the concentrations of hopanes and $n$-alkanes was found. The distribution pattern and characteristics of hopanes indicated that vehicle emission was an important source of the organic matter in PM$_{2.5}$ in Yiwu City.