Abstract: A comprehensive field campaign regarding atmospheric aerosol and chemistry was conducted in suburban Tianjin, from July 11 to August 14, 2009. The dataset of particle number size distributions (0.02?1.00 μm in diameter) was analyzed and parameterized, and was further studied with respect to its diurnal variation and relations with meteorological parameters such as wind speed and wind direction. The hourly-averaged integrated number and volume concentrations are 1.7×10⁴cm^-3 and 59 μm³/cm³ respectively. A diurnal variation of particle number concentration is observed with three peaks (06:00?08:00, 13:00?15:00, and 19:00?21:00), which are highly influenced by traffic density and photochemical nucleation process. Maxima of particle concentration occur with calm winds and show no dependency on wind directions, which suggests that local emission sources contribute mostly to the aerosol pollution. Particle number concentration decreases when wind speed increases, and obtains in a relatively high level when wind from S/SW/SE directions prevails, which implies that local particle concentration is influenced by transport from more polluted areas in the south.

Key words: particle number size distribution, log-normal fitting, diurnal variation

摘要： 2009年7月11日到8月14日, 在天津市武清区对粒径在0.02~1.00 μm范围内的气溶胶粒子谱分布进行了连续观测。在对气溶胶谱分布资料进行详细统计分析和参数化的基础上, 研究了其日变化规律及其与风速、风向等气象条件的关系。在该粒径范围内, 气溶胶粒子数浓度的平均值为1.7×10⁴cm^-3, 体积浓度的平均值为59 μm³/cm³。气溶胶的数浓度和谱分布具有明显的日变化规律, 粒子数浓度在道路交通的早晚高峰期间和午后太阳辐射最强的时间段出现峰值, 这与道路上机动车的排放和光化学反应中的气?粒转化过程密切相关。局地风速和风向对气溶胶浓度有显著影响。总体而言, 粒子浓度的高值均出现在低风速条件下, 与风向没有明显的依赖关系, 这说明本地源排放是粒子的重要来源。粒子浓度随着风速增加而降低, 且在盛行南风时出现相对高值, 这说明当地受到来自南部较污染地区输送的影响。

关键词: 气溶胶谱分布, 对数正态拟合, 日变化