北京城市道路积尘多环芳烃的粒度分布特征及其影响因素

对北京城市不同道路类型的道路积尘进行了为期16个月的采样,分别分析了道路尘的粒径、多环芳烃及TOC.道路积尘的粒径呈三峰态分布,<75 μm部分的颗粒所占体积最大,>214 μm部分颗粒所占体积最小.>214 μm这部分颗粒中的多环芳烃质量分数最低,<75μm和75～214μm这两部分颗粒中多环芳烃的质量分数没有显著差异,但由于<75μm部分颗粒所占的体积和质量比例最大,这部分颗粒的多环芳烃累积量所占比例最高.不同道路的积尘粒径存在差异,海淀路和成府路机动车道的积尘颗粒相比自行车道和人行道的颗粒更粗.由于粒径分布的差异和多环芳烃质量分数的差异,不同类型道路的多环芳烃累积量的粒径分布呈现差异.多环芳烃质量分数和累积量的粒度分布也呈现季节差异,冬春季<75 μm颗粒中的多环芳烃质量分数最高,多环芳烃的累积量所占比例也较夏秋季高.在三个粒级中,TOC与多环芳烃质量分数均呈现显著的正相关.高比例的细颗粒及细颗粒中的多环芳烃使得道路积尘再悬浮进入大气以及随湿沉降进入地表径流的环境风险加大.

Size distribution and influencing factors of road dust PAHs in Beijing, China

Road dust for different types of traffic roads was collected monthly for 16 months in Beijing. Size distribution of PAHs and TOC of road dust were investigated. The size distribution of road dust showed a trimodal spectrum. The particles of<75 μm and >214 μm constituted the highest and lowest percentage by volume, respectively. No significant difference was found for PAHs be-tween the fractions of<75 μm and 75～214 μm. While PAHs content was lowest in >214 μm fraction, <75 μm fraction contributed the highest percentage of total PAHs. Size distribution of dust was found to be different among different types of roads, and the sizes of dusts in vehicle lane of Haidian Road and Chengfu Road were larger than bicycle lane and sidewalk. As a result of the variations of PAHs content and size distribution of dust, the size distribution of accumulated PAHs varied among different types of roads. The size distributions of PAHs accumulation varied with seasons. For <75 μm fraction, the road dust had a higher PAHs content and con-tributed higher percentage of total PAHs in winter and spring. For all the three size fractions, TOC revealed a significant positive correlation with PAHs content.