Brook Jeffrey R, Dann Tom F, Bonvalot Yvette
a Atmospheric Environment Service , Downsview , Ontario , Canada.
b Environment Canada , Ottawa , Ontario , Canada.
J Air Waste Manag Assoc. 1999 Sep;49(9):35-44. doi: 10.1080/10473289.1999.10463884.
Canadian particle monitoring programs examining PM10, PM2.5, and particle composition have been in operation for over 10 years. Until recently, the measurements were manual/filter-based with 24-hr sample collection varying in frequency from daily to every sixth day, using GrasebyAnderson dichotomous samplers. In the past few years, these monitoring activities have been expanded to include hourly measurements using tapered element oscillating microbalances (TEOMs). This continuous monitoring program started operation focusing on PM but now emphasizes PM through the addition of more TEOMs and switching of the inlets of some of the existing units. The data from all of these measurement activities show that there are broad geographical differences and also local- to regional-scale spatial differences in mass and composition of PM2.5. Due to variations in sources, significantly different PM2.5 concentrations are not uncommon within the same city. Comparison of nearby urban and rural sites indicates that 30 and 40% of the PM is from local urban sources in Montreal and Toronto, respectively. Hourly PM measurements in Toronto suggest that vehicular emissions are an important contributor to urban PM There has been a decreasing trend in urban PM with annual average concentrations between the 1987-1990 and 1993-1995 periods decreasing by 11 to 39%, depending upon the site. The largest declines were in Montreal and Halifax, and the smallest decline was in Toronto. Comparison of 24-hr TEOM and manual dichotomous sampler PM measurements from a site in Toronto indicates that the TEOM results in lower concentrations. The magnitude of this difference is relatively small in the warmer months, averaging about 12%. During the colder months the difference averages about 23%, but can be as large as 50%.
加拿大针对细颗粒物（PM10）、超细颗粒物（PM2.5）及颗粒物成分的监测项目已开展了10多年。直到最近，测量工作还是基于手动/滤膜方式，使用格拉斯比-安德森二分采样器，每24小时采样一次，采样频率从每天一次到每六天一次不等。在过去几年里，这些监测活动已扩大到包括使用锥形元件振荡微天平（TEOM）进行每小时测量。这个连续监测项目开始时侧重于细颗粒物监测，但现在通过增加更多的TEOM以及更换一些现有监测设备的进气口，转而强调超细颗粒物监测。所有这些测量活动的数据表明，在超细颗粒物的质量和成分方面，存在广泛的地理差异以及从局部到区域尺度的空间差异。由于污染源的不同，在同一个城市内，细颗粒物浓度显著不同的情况并不罕见。对附近城市和农村监测点的比较表明，在蒙特利尔和多伦多，分别有30%和40%的细颗粒物来自当地城市源。多伦多的每小时细颗粒物测量结果表明，车辆排放是城市细颗粒物的一个重要来源。城市细颗粒物呈下降趋势，1987 - 1990年和1993 - 1995年期间的年平均浓度下降了11%至39%，具体降幅取决于监测点。降幅最大的是蒙特利尔和哈利法克斯，降幅最小的是多伦多。对多伦多一个监测点的24小时TEOM测量结果与手动二分采样器测量的细颗粒物结果进行比较表明，TEOM测量得出的浓度较低。在较温暖的月份，这种差异的幅度相对较小，平均约为12%。在较寒冷的月份，差异平均约为23%，但可能高达50%。
