Interpretation of particle number size distributions measured across an urban area during the FASTER campaign
Interpretation of particle number size distributions measured across an urban area during the FASTER campaign
复制标题
DOI：
10.5194/acp-19-39-2019
复制
发表时间：
2019-01-03
影响因子：
6.3
通讯作者：
Grimmond, Sue
中科院分区：
文献类型：
--
作者：
Harrison, Roy M.;Beddows, David C. S.;Grimmond, Sue
2017 年 1 月至 2 月，在伦敦市中心的五个地点进行了为期 1 个月的活动，通过扫描移动粒径测定仪 (SMPS) 同时测量了颗粒数量分布。这些测量还配有凝结粒子计数器 (CPC)，用于测量其中四个地点的总颗粒数计数，并使用气体浓度计在五个地点测量黑碳 (BC)。详细分析了粒度分布和 SMPS 总数与 CPC 总数和黑炭测量的空间分布和相互关系以及粒度分布的变化。一个地点（马里波恩路）位于交通繁忙的街道峡谷中，一个地点（威斯敏斯特大学）位于马里波恩路采样器附近的屋顶上，另一个采样器位于马里波恩路以北的一个主要公园内的摄政大学。第四个采样器位于 BT 塔附近距地面 160 m 的位置，第五个采样器位于北肯辛顿主要采样区以西 4 公里处。与早期的研究一致，我们发现摄政大学（公园）场地的尺寸分布模式已转向更小的尺寸，平均颗粒收缩率为 0.04 nm s(-1)，在低风速时该值略低，在高风速时该值稍大。有证据表明，在高架 BT 塔现场的某些条件下，半挥发成核模式完全蒸发。虽然 SMPS 总计数和黑炭显示出典型的以流量为主的昼夜分布，但 CPC 计数数据通常在夜间达到峰值，CPC/SMPS 和 CPC/BC 比率也是如此。这被认为是由于存在高浓度的小颗粒（直径 2.5-15 nm），可能是由于夜间凉爽条件下交通排放的凝结增长而产生的。这种行为在摄政大学和威斯敏斯特大学站点最为明显，而在马里波恩路则不太明显，而在高架英国电信塔站点，颗粒物数量 (CPC) 与黑碳的比率在早高峰期间达到峰值，而不是在夜间，这与其他站点不同。尽管距伦敦市中心 22 公里，但与西风和 WSW 扇区的风相关的成核模式粒子的升高被认为是由伦敦希思罗机场的排放造成的。
Particle number size distributions have been measured simultaneously by scanning mobility particle sizers (SMPSs) at five sites in central London for a 1 month campaign in January-February 2017. These measurements were accompanied by condensation particle counters (CPCs) to measure total particle number count at four of the sites and Aethalometers measuring black carbon (BC) at five sites. The spatial distribution and inter-relationships of the particle size distribution and SMPS total number counts with CPC total number counts and black carbon measurements have been analysed in detail as well as variations in the size distributions. One site (Marylebone Road) was in a street canyon with heavy traffic, one site (Westminster University) was on a rooftop adjacent to the Marylebone Road sampler, and a further sampler was located at Regent's University within a major park to the north of Marylebone Road. A fourth sampler was located nearby at 160 m above ground level on the BT tower and a fifth sampler was located 4 km to the west of the main sampling region at North Kensington. Consistent with earlier studies it was found that the mode in the size distribution had shifted to smaller sizes at the Regent's University (park) site, the mean particle shrinkage rate being 0.04 nm s(-1) with slightly lower values at low wind speeds and some larger values at higher wind speeds. There was evidence of complete evaporation of the semi-volatile nucleation mode under certain conditions at the elevated BT Tower site. While the SMPS total count and black carbon showed typical traffic-dominated diurnal profiles, the CPC count data typically peaked during night-time as did CPC/SMPS and CPC/BC ratios. This is thought to be due to the presence of high concentrations of small particles (2.5-15 nm diameter) probably arising from condensational growth from traffic emissions during the cooler night-time conditions. Such behaviour was most marked at the Regent's University and Westminster University sites and less so at Marylebone Road, while at the elevated BT Tower site the ratio of particle number (CPC) to black carbon peaked during the morning rush hour and not at night-time, unlike the other sites. An elevation in nucleation mode particles associated with winds from the west and WSW sector was concluded to result from emissions from London Heathrow Airport, despite a distance of 22 km from the central London sites.