Kozawa Kathleen H, Winer Arthur M, Fruin Scott A
California Air Resources Board, Research Division, 1001 I Street, Sacramento, CA 95814, USA.
Environmental Science and Engineering Program, Department of Environmental Health Sciences, School of Public Health, University of California, 650 Charles E. Young Drive South #46-081 CHS, Los Angeles, CA 90095-1772, USA.
Atmos Environ (1994). 2012 Dec;63:250-260. doi: 10.1016/j.atmosenv.2012.09.045.
High ambient ultrafine particle (UFP) concentrations may play an important role in the adverse health effects associated with living near busy roadways. However, UFP size distributions change rapidly as vehicle emissions dilute and age. These size changes can influence UFP lung deposition rates and dose because deposition in the respiratory system is a strong function of particle size. Few studies to date have measured and characterized changes in near-road UFP size distributions in real-time, thus missing transient variations in size distribution due to short-term fluctuations in wind speed, direction, or particle dynamics. In this study we measured important wind direction effects on near-freeway UFP size distributions and gradients using a mobile platform with 5-s time resolution. Compared to more commonly measured perpendicular (downwind) conditions, parallel wind conditions appeared to promote formation of broader and larger size distributions of roughly one-half the particle concentration. Particles during more parallel wind conditions also changed less in size with downwind distance and the fraction of lung-deposited particle number was calculated to be 15% lower than for downwind conditions, giving a combined decrease of about 60%. In addition, a multivariate analysis of several variables found meteorology, particularly wind direction and temperature, to be important in predicting UFP concentrations within 150 m of a freeway ( = 0.46, = 0.014).
高环境超细颗粒物（UFP）浓度可能在与居住在繁忙道路附近相关的不良健康影响中起重要作用。然而，随着车辆排放物的稀释和老化，UFP的粒径分布会迅速变化。这些粒径变化会影响UFP在肺部的沉积率和剂量，因为在呼吸系统中的沉积是粒径的强函数。迄今为止，很少有研究实时测量和表征近道路UFP粒径分布的变化，因此错过了由于风速、风向或颗粒物动力学的短期波动导致的粒径分布的瞬态变化。在本研究中，我们使用具有5秒时间分辨率的移动平台测量了风向对高速公路附近UFP粒径分布和梯度的重要影响。与更常测量的垂直（顺风）条件相比，平行风条件似乎促进了更宽、更大粒径分布的形成，颗粒物浓度约为垂直条件下的一半。在更平行的风条件下，颗粒物粒径随顺风距离的变化也较小，计算得出肺部沉积的颗粒数比例比顺风条件下低15%，综合降低约60%。此外，对几个变量的多变量分析发现，气象条件，特别是风向和温度，对于预测高速公路150米范围内的UFP浓度很重要（ = 0.46， = 0.014）。
