秋季嘉兴PM2.5质量浓度特征分析

利用膜采样、颗粒在线称重方法和维萨拉气象仪对2004和2006年秋季嘉兴大气中ρ(PM_2.5)及气象因子进行了分析.结果表明:2004和2006年秋季ρ(PM2.5)分别为(84.7±62.4)和(89.0±61.5) 　μg/m3；ρ(PM2.5)占ρ(PM₁₀) 比例为42%～69%；ρ(PM_2.5)日均值变化大(16.7～345.7 μg/m3)，晴天ρ(PM_2.5)约为阴雨天的2倍.ρ(PM_2.5)日变化分析表明，晴天呈双峰双谷现象，晚高峰(16:00—20:00)ρ(PM_2.5)大于早高峰(06:00—10:00)，阴雨天日变化不明显.PM_2.5与相对湿度无显著相关性，但在不同相对湿度下PM_2.5与能见度呈显著的负指数关系.东北风和西北风是观测期内当地的主导风向，ρ(PM2.5)高值出现在西南风方向，重污染天气过程形成原因复杂. 

Mass Concentration Characters of PM2.5 in Autumn in Jiaxing

Fine particles (PM_2.5) and meteorological data weremeasured by filter sampling, online particle measurer and Vaisala meteorological instrument in the autumn of 2004 and 2006 in Jiaxing. The results showed that the averagemass concentration of PM_2.5 in the autumn was (84.7±62.4) μg/m3 in 2004 and (89.0±61.5) μg/m3 in 2006, the proportion of PM_2.5 in PM₁₀ was 42%～69%, and that the daily average mass concentration of PM_2.5 ranged from 16.7 to 345.7　μg/m3. The mass concentration of PM_2.5 in sunny days was about twice of that in rainy days. The trend of the diurnal variation of PM_2.5 was bimodal distribution in sunny days, with the second peak appearing during 16:00 to 20:00 higher than thefirst peak appeared during 06:00 to　10:00, and with no apparent diurnal variationin rainy days. The relationship between Relative Humidity (RH) and PM2.5 was not obvious, while the relationship between PM_2.5 and visibility was different under different RH. The North West and North East was the main winddirection during experiment at the site, and the pollution source of PM2.5 was mainly from South West transport. The mechanism of heavy pollution process was complex.