Diurnal variation characteristics of PM_(10) mass concentration from traffic exhaust emission and its influencing factors on street air quality in Beijing
CHENG Xing-hong1,2, XU Xiang-de1, DING Guo-an1, CHAN C Y3, WONG K H3, L Hai4(1 State Key Laboratory of Severe Weather (LaSW), Chinese Academy of Meteorology Science, Beijing 100081, China; 2 Graduate University of Chinese Academy of Sciences, Beijing 100039, China; 3 Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong; 4 Meteorological Observatory, Guiyang Meteorological Bureau, Guiyang 550002, China)
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.