| 街道峡谷内超细颗粒数浓度和粒径分布特征试验研究 |
| 摘要点击 1434 全文点击 1410 投稿时间：2006-05-27 修订日期：2006-08-05 |
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| 中文关键词 街道峡谷 超细颗粒 数浓度 粒径分布 垂直衰减率 |
| 英文关键词 street canyon ultrafine particle number concentration size distribution vertical decay rate |
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| 中文摘要 |
| 测试研究了街道峡谷内4个不同高度处10～487 nm粒径范围内颗粒的数浓度及粒径分布，根据特定条件下的测量结果，得到不同高度处颗粒数浓度粒径分布均呈包含2～3个峰的对数正态分布；一定高度范围内（15～20 m），随高度增加, 核模态数浓度显著降低，其峰值粒径向大粒子方向偏移，积聚模态数浓度和粒径分布变化不如核模显著；随高度继续增大，颗粒数浓度和粒径分布无显著变化.同时对不同测点的PM2.5和CO的浓度进行了测试，得到总颗粒数、总颗粒体积、CO和PM2.5浓度垂直方向多呈幂函数递减规律分布.受环境风速风向影响，测试Ⅰ（高风速，递升型街道峡谷）时总颗粒体积、PM2.5和CO浓度均低于测试Ⅱ（低风速，风向平行于街道峡谷）时，测试Ⅰ时总颗粒数、总颗粒体积、PM2.5和CO浓度的垂直衰减率均低于测试Ⅱ时；无论递升型街道峡谷或风向平行于街道峡谷，总颗粒数浓度垂直衰减率均大于同期CO和PM2.5的垂直衰减率，表明总颗粒数浓度除了受环境空气的稀释作用影响外，同时还受到沉降或凝并等作用的影响. |
| 英文摘要 |
| A field experiment was conducted to measure concentrations and size distributions of particle (10 nm<DP<487 nm) at four heights in an asymmetric street canyon on Beijing East Road in Shanghai, China. It shows that particle number size distributions are bimodal or trimodal lognormal in form. At a certain height in the range from 15 to 20 m, particle number concentrations and size distributions significantly vary with the height. Particle number concentrations in nuclei mode drop significantly and the mode diameters shift to the larger diameter. The variations of particle number concentration and size distribution in accumulation mode are less significant than that in nuclei mode. Particle number concentrations and size distributions slightly change with increasing the height in the range from 20 to 38 m. Concentrations of CO and PM2.5 were also measured. Power laws are found to be well fitted for the concentration decay of total particle number, total particle volume, CO and PM2.5Due to the effect of the wind speed and direction, the total particle volume, PM2.5 and CO concentrations are lower for Test Ⅰ (high wind speed and step-up street canyon) than for test Ⅱ (low wind speed and wind channeling along the canyon), at the meantime, the decay rates of the total particle number, the total particle volume, CO and PM2.5 concentrations for test Ⅰare lower than for test Ⅱ. No matter how the wind direction changes, the decay rates of the total particle number concentrations are larger than those of CO and PM2.5, which clearly shows that coagulation and deposition besides dilution processes affect the total particle number concentration. |
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