Tong Zheming, Whitlow Thomas H, MacRae Patrick F, Landers Andrew J, Harada Yoshiki
Department of Mechanical and Aerospace Engineering, Cornell University, Gruman Hall, Ithaca, NY, USA.
Section of Horticulture, School of Integrative Plant Science, Cornell University, Room 23 Plant Science Building, Ithaca, NY 14853, USA.
Environ Pollut. 2015 Jun;201:141-9. doi: 10.1016/j.envpol.2015.02.026. Epub 2015 Mar 20.
Many reports of trees' impacts on urban air quality neglect pattern and process at the landscape scale. Here, we describe brief campaigns to quantify the effect of trees on the dispersion of airborne particulates using high time resolution measurements along short transects away from roads. Campaigns near major highways in Queens, NY showed frequent, stochastic spikes in PM2.5. The polydisperse PM2.5 class poorly represented the behavior of discrete classes. A transect across a lawn with trees had fewer spikes in PM2.5 concentration but decreased more gradually than a transect crossing a treeless lawn. This coincided with decreased Turbulence Kinetic Energy downwind of trees, indicating recirculation, longer residence times and decreased dispersion. Simply planting trees can increase local pollution concentrations, which is a special concern if the intent is to protect vulnerable populations. Emphasizing deposition to leaf surfaces obscures the dominant impact of aerodynamics on local concentration.
许多关于树木对城市空气质量影响的报告都忽略了景观尺度上的格局和过程。在此，我们描述了一些简短的活动，通过沿着远离道路的短横断面进行高时间分辨率测量，来量化树木对空气中颗粒物扩散的影响。在纽约皇后区主要高速公路附近开展的活动显示，PM2.5中频繁出现随机峰值。多分散的PM2.5类别不能很好地代表离散类别的行为。一条穿过有树木草坪的横断面，其PM2.5浓度峰值较少，但下降速度比穿过无树木草坪的横断面更平缓。这与树木下风方向湍流动能的降低相吻合，表明存在再循环、更长的停留时间和更低的扩散。单纯种树可能会增加局部污染浓度，如果目的是保护弱势群体，这是一个特别值得关注的问题。强调颗粒物在树叶表面的沉积掩盖了空气动力学对局部浓度的主要影响。
