Li Xin-Ling, Huang Zhen, Wang Jia-Song, Tu Xiao-Dong, Ye Chun
Center for Combustion and Environmental and Technology, Shanghai Jiaotong University, Shanghai 200030, China.
Huan Jing Ke Xue. 2007 Apr;28(4):695-700.
A field experiment was conducted to measure concentrations and size distributions of particle (10 nm < D(p) < 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 1.5 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 PM(2.5) were also measured. Power laws are found to be well fitted for the concentration decay of total particle number, total particle volume, CO and PM(2.5). Due to the effect of the wind speed and direction, the total particle volume, PM(2.5) 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 PM(2.5) concentrations for test I are 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 PM(2.5), which clearly shows that coagulation and deposition besides dilution processes affect the total particle number concentration.
在中国上海北京东路的一个不对称街道峡谷中，进行了一项实地实验，以测量四个高度处粒径范围为10纳米＜D(p)＜487纳米的颗粒物浓度和粒径分布。结果表明，颗粒物数量粒径分布呈双峰或三峰对数正态分布形式。在1.5至20米范围内的某一高度，颗粒物数量浓度和粒径分布随高度显著变化。核模态中的颗粒物数量浓度显著下降，模态直径向较大直径偏移。积聚模态中颗粒物数量浓度和粒径分布的变化不如核模态中显著。在20至38米范围内，颗粒物数量浓度和粒径分布随高度增加略有变化。还测量了CO和PM(2.5)的浓度。发现幂律能很好地拟合总颗粒物数量、总颗粒物体积、CO和PM(2.5)的浓度衰减。由于风速和风向的影响，实验I（高风速和阶梯状街道峡谷）的总颗粒物体积、PM(2.5)和CO浓度低于实验II（低风速和沿峡谷的风道效应），同时，实验I的总颗粒物数量、总颗粒物体积、CO和PM(2.5)浓度的衰减率低于实验II。无论风向如何变化，总颗粒物数量浓度的衰减率都大于CO和PM(2.5)的衰减率，这清楚地表明除稀释过程外，凝聚和沉降也会影响总颗粒物数量浓度。
