| 不同交通状况下道路边大气颗粒物数浓度粒径分布特征 |
| 摘要点击 2906 全文点击 1729 修订日期：2011-05-19 |
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| 中文关键词 超细颗粒物 数浓度 粒径分布 交通环境 交通流 |
| 英文关键词 ultrafine particles number concentration size distribution roadside microenvironment traffic flow |
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| 中文摘要 |
| 研究了不同交通状况下北京交通环境大气颗粒物数浓度的污染特征.应用扫描电迁移率颗粒粒径谱仪(SMPS)测定了2009年8月常规交通状况和2008年8月奥运交通状况下北四环道路边大气颗粒物的数浓度,分析了数浓度的粒径分布特征及其逐时变化规律,目的为辨析交通流改变对交通环境中颗粒物数浓度的影响.常规交通状况下道路边超细颗粒物(10~100 nm)和10~478 nm颗粒物总粒数浓度分别为(1.15±0.49)×104 个·cm-3、(1.61±0.57)×104 个·cm-3,奥运交通状况下分别下降到(0.55±0.14)×104 个·cm-3、(1.21±0.24)×104 个·cm-3,不同粒径段中超细颗粒物数浓度降幅最高,为52.2%.常规交通状况下道路边大气中颗粒物粒数浓度呈双峰分布,峰值粒径依次为22.5 nm和113.0 nm.奥运期间由于机动车单双号限行和黄标车禁行等措施的实施, 22.5 nm处颗粒物数浓度峰值消失.粒径分布逐时变化显示,常规交通状况下00:00~04:00柴油车流量高峰、11:00~13:00高温强光照和17:00~20:00交通晚高峰这3个时段内超细颗粒物数浓度较高; 而奥运期间受到交通流量下降、平均车速提高等因素影响,道路边颗粒物数浓度粒径分布逐时变化趋于平缓. |
| 英文摘要 |
| The profiles of number concentration of ambient particles at a roadside site in Beijing were studied with different traffic conditions. A Scanning Mobility Particle Sizer (SMPS) was utilized to measure the number concentrations of fine and ultrafine (10-100 nm) particles in August 2008 and August 2009, which represented the normal and Olympic traffic conditions, respectively. Size distributions of particle number concentration were identified and their temporal variations were also discussed. Results indicated that with normal traffic pattern, the total number concentration of ultrafine and 10-478 nm particles were (1.15±0.49)×104 cm-3 and (1.61±0.57)×104 cm-3,respectively. While the concentrations were decreased to (0.55±0.14)×104 cm-3 and (1.21±0.24)×104 cm-3, respectively, with special traffic condition during the Beijing Olympic Games. Largest reduction of 52.2% was observed for ultrafine particles among all size ranges. With normal traffic condition, bimodal distribution was found with two peak values in number concentrations around 22.5 nm and 113.0 nm. During the Olympic period, nucleation mode particles were significantly reduced due to a series of temporal control measures on motor vehicles such as the removal of yellow-labeled vehicles from the roads and travel restrictions based on odd-even license plate numbers. As a result, the peak in particle number concentration at 22.5 nm disappeared. The temporal variation indicated that significantly higher ultrafine particle number concentrations occurred around 00:00-04:00, 11:00-13:00 and 17:00-20:00 with normal traffic situation, which primarily attributed to the contributions of diesel exhaust at night, secondary formation at noon and traffic jam in the evening, respectively. However during the Olympic period, the temporal variation pattern changed significantly. The gap in the number concentrations of ultrafine particle between these three time periods and other time periods were narrowed, which should be attributed to the reduction of traffic flow as well as the increase of fleet speed during the Olympics. |
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