北京市城市街区PM10浓度日变化特征及其影响因子

为了解北京城市街区PM10浓度日变化特征及其影响因素,利用2003年10月BECAPEX(Beijing City Air Pollution Experiment)街道、街区及周边小区4个测点PM10浓度的对比观测试验资料和同期街道机动车流量、采样点附近自动气象站风速及探空资料进行了综合对比分析.通过天气诊断和统计学分析相结合,初步分析了北京市城区街道大气污染物PM10浓度日变化特征及机动车排放污染、气象条件对PM10浓度日变化的影响.结果表明,试验期间北京市城区街道PM10浓度日变化特征存在明显差异,交通源污染物PM10浓度日变化具有单峰与双峰型差异的特殊性.工作日PM10浓度日变化出现双峰,周末PM10浓度日变化仅有单峰出现; 交通污染源和气象条件对城市街区PM10浓度日变化特征的影响程度存在空间差异.离交通污染源较近的街区PM10浓度日变化受机动车排放污染的影响程度较大,而离交通源较远的小区PM10浓度受机动车排放污染的影响相对较小; 不稳定天气条件下交通污染源影响范围较小,在特定天气条件下,气象条件的影响强度可显著超过交通污染源的影响.

Diurnal variation characteristics of PM10 mass concentration from traffic exhaust emission and its influencing factors on street air quality in Beijing

The article aims to introduce our research on PM10 based on the samples we have collected at four parallel sampling sites during the three days of Oct. 17 to Oct. 19, 2003, with the purpose to analyze the diurnal variation characteristics of PM10 mass concentration caused by the traffic. In the article, we also made a preliminary discussion on the influential factors, such as the exhaust emission and meteorological conditions, such as atmospheric stability, wind speed and cloud condition based on the traffic flow amount, AWS (Automatic Weather Station) wind speed and the upper-strata air data detected during the same period. The four sampling sites chosen by us are all located at No.33#, South Street, Zhongguancun Road, Beijing near China State Library, (Point A). The following results revealed that the diurnal variation characteristics of PM10 mass concentration vary due to the traffic. Difference between the two kinds of diurnal variation characteristics of PM10 proves obvious during the sampling period. That is, the diurnal variation of PM10 during the workdays indicates double-peaked whereas that of PM10 on the weekend is single-peaked. Thus, it can be concluded that the diurnal variation characteristics of PM10 are affected greatly by the vehicle flow amount at daytime. In addition, it can be found that the affecting range and intensity of the traffic exhaust emission change with the distance from traffic emission sources. Along with the traffic exhaust emission, meteorological factors in the boundary layer have also had strong impact on the diurnal variation characteristics of PM10 concentration, such as weather condition, atmospheric stability, and wind speed.