Kumar Prashant, Fennell Paul, Britter Rex
Department of Engineering, University of Cambridge, CB2 1PZ Cambridge, UK.
Sci Total Environ. 2008 Feb 15;390(2-3):437-47. doi: 10.1016/j.scitotenv.2007.10.013. Epub 2007 Nov 13.
A newly developed instrument, the 'fast response differential mobility spectrometer (DMS500)', was deployed to measure the particles in the 5-1000 nm range in a Cambridge (UK) street canyon. Measurements were taken for 7 weekdays (from 09:00 to 19:00 h) between 8 and 21 June 2006 at three heights close to the road level (i.e. 0.20 m, 1.0 m and 2.60 m). The main aims of the measurements were to investigate the dependence of particle number distributions (PNDs) and concentrations (PNCs) and their vertical variations on wind speed, wind direction, traffic volume, and to estimate the particle number flux (PNF) and the particle number emission factors (PNEF) for typical urban streets and driving conditions. Traffic was the main source of particles at the measurement site. Measured PNCs were inversely proportional to the reference wind speed and directly proportional to the traffic volume. During the periods of cross-canyon flow the PNCs were larger on the leeward side than the windward side of the street canyon showing a possible effect of the vortex circulation. The largest PNCs were unsurprisingly near to road level and the pollution sources. The PNCs measured at 0.20 m and 1.0 m were the same to within 0.5-12.5% indicating a well-mixed region and this was presumably due to the enhanced mixing from traffic produced turbulence. The PNCs at 2.60 m were lower by 10-40% than those at 0.20 m and 1.0 m, suggesting a possible concentration gradient in the upper part of the canyon. The PNFs were estimated using an idealised and an operational approach; they were directly proportional to the traffic volume confirming the traffic to be the main source of particles. The PNEF were estimated using an inverse modelling technique; the reported values were within a factor of 3 of those published in similar studies.
一种新开发的仪器——“快速响应差分迁移率光谱仪（DMS500）”，被部署用于测量英国剑桥一条街道峡谷中5 - 1000纳米范围内的颗粒物。在2006年6月8日至21日的7个工作日（09:00至19:00），于靠近路面的三个高度（即0.20米、1.0米和2.60米）进行了测量。测量的主要目的是研究颗粒物数量分布（PNDs）和浓度（PNCs）及其垂直变化对风速、风向、交通流量的依赖性，并估算典型城市街道和驾驶条件下的颗粒物数量通量（PNF）和颗粒物数量排放因子（PNEF）。交通是测量地点颗粒物的主要来源。测量得到的PNCs与参考风速成反比，与交通流量成正比。在峡谷交叉气流期间，街道峡谷背风侧的PNCs比迎风侧大，显示出涡旋环流可能产生的影响。最大的PNCs不出所料地靠近路面和污染源。在0.20米和1.0米处测量的PNCs在0.5 - 12.5%的范围内相同，表明存在一个充分混合的区域，这可能是由于交通产生的湍流增强了混合。2.60米处的PNCs比0.20米和1.0米处低10 - 40%，表明峡谷上部可能存在浓度梯度。PNFs使用理想化方法和实用方法进行估算；它们与交通流量成正比，证实了交通是颗粒物的主要来源。PNEFs使用反演建模技术进行估算；报告的值与类似研究中公布的值相差在3倍以内。
