中文摘要：

下垫面高度梯度对城市颗粒污染物的地球化学循环有重要的影响,不同高度下垫面上累积的灰尘可能对城市地表径流与大气颗粒物污染有重要指示作用.本文以不同高度梯度的下垫面,如路面（0 m）、公交站台（3 m）、天桥（5 m）、楼顶（20 m）上的灰尘为研究对象,揭示高度梯度对灰尘颗粒物单位面积质量、粒径组成、重金属含量和粒径污染负荷比的影响.结果表明,随着高度梯度变化,不同下垫面上灰尘颗粒物的单位面积质量之间存在显著差异（p〈0.05）：路面（（33.0±27.1）g·m^-2）〉楼顶（（20.6±11.7）g·m^-2）〉天桥（（4.4±4.0）g·m^-2）〉公交站台（（2.3±1.4）g·m^-2）;高度梯度对细灰尘（粒径〈105μm）的质量比的影响为：公交站台（49.5%）〉楼顶（40.8%）〉路面（38.6%）〉天桥（37.6%）;6种重金属在不同高度下垫面的含量不同,其中,Cr、Cu和Ni在公交站台含量最高,Cd和Pb在楼顶含量最高,6种金属（除Cu外）均在路面含量最低.细灰尘（〈105μm）所占颗粒物污染负荷比为：公交站台（67.4%）〉楼顶（49.6%）〉天桥（49.2%）〉路面（48.1%）.临时性管控措施（限行、限产等）和常规性清扫（人工清扫和机械清扫）均能减少灰尘质量,使细灰尘质量比增加,重金属污染负荷有明显削减,但对城市管理来说,后者更经济实用.

英文摘要：

The height of the depositional surface has an important influence on the geochemical signature of urban dust. The accumulation of different dust types on surfaces at different heights may in turn affect urban surface runoff and atmospheric particulate pollution. This study analyzed the influence of depositional height of various surfaces（ road surface,platform,overbridge,and rooftop） on the content and size fraction of heavy metals in urban dusts.The results showed that there were significant differences among the amounts of dust at different heights（ P〈0.05）. In particular,the amounts of dust on the road surface,platform,overbridge,and roof were（ 33. 0 ± 27. 1）,（ 2. 3 ± 1. 4）,（ 4. 4 ± 4. 0） and（ 20. 6 ± 11. 7） g·m^-2,respectively. The mass percentage of fine dust（ with particle size105 μm） was the greatest on the platform（ 49.5%）,followed by roof（ 40.8%）,road surface（ 38.6%）,and overbridge（ 37.6%）. The contents of six heavy metals（ Cd,Cr,Cu,Ni,Pb,and Zn） also were distinct at different heights. In particular,the contents of Cr,Cu and Ni were the highest in platform dust,but Cd and Pb were the highest in roof dust. All heavy metals except Cu were the lowest in road surface dust. The contribution of heavy metals to the fine dust fraction was the greatest for the platform（ 67.4%）,followed by roof（ 49.6%）,overbridge（ 49.2%）,and road surface（ 48.1%）. Temporary control measures such as limiting car usage and industrial production as well as routine manual and mechanical cleaning can reduce the amount of dust and its pollution loading of heavy metals while increasing the fine dust mass ratio. For a city administration＇s perspective,routine cleaning is more practical.