Celo Valbona, Yassine Mahmoud M, Dabek-Zlotorzynska Ewa
Analysis and Air Quality Section, Air Quality Research Division, Science and Technology Branch, Environment and Climate Change Canada, 335 River Road, Ottawa, ON K1A 0H3, Canada.
Toxics. 2021 Oct 14;9(10):264. doi: 10.3390/toxics9100264.
Traffic is a significant pollution source in cities and has caused various health and environmental concerns worldwide. Therefore, an improved understanding of traffic impacts on particle concentrations and their components could help mitigate air pollution. In this study, the characteristics and sources of trace elements in PM (fine), and PM (coarse), were investigated in dense traffic areas in Toronto and Vancouver, Canada, from 2015-2017. At nearby urban background sites, 24-h integrated PM samples were also concurrently collected. The PM and PM masses, and a number of elements (i.e., Fe, Ba, Cu, Sb, Zn, Cr), showed clear increases at each near-road site, related to the traffic emissions resulting from resuspension and/or abrasion sources. The trace elements showed a clear partitioning trend between PM and PM, thus reflecting the origin of some of these elements. The application of positive matrix factorization (PMF) to the combined fine and coarse metal data (86 total), with 24 observations at each site, was used to determine the contribution of different sources to the total metal concentrations in fine and coarse PM. Four major sources were identified by the PMF model, including two traffic non-exhaust (crustal/road dust, brake/tire wear) sources, along with regional and local industrial sources. Source apportionment indicated that the resuspended crustal/road dust factor was the dominant contributor to the total coarse-bound trace element (i.e., Fe, Ti, Ba, Cu, Zn, Sb, Cr) concentrations produced by vehicular exhaust and non-exhaust traffic-related processes that have been deposited onto the surface. The second non-exhaust factor related to brake/tire wear abrasion accounted for a considerable portion of the fine and coarse elemental (i.e., Ba, Fe, Cu, Zn, Sb) mass at both near-road sites. Regional and local industry contributed mostly to the fine elemental (i.e., S, As, Se, Cd, Pb) concentrations. Overall, the results show that non-exhaust traffic-related processes were major contributors to the various redox-active metal species (i.e., Fe, Cu) in both PM fractions. In addition, a substantial proportion of these metals in PM was water-soluble, which is an important contributor to the formation of reactive oxygen species and, thus, may lead to oxidative damage to cells in the human body. It appears that controlling traffic non-exhaust-related metals emissions, in the absence of significant point sources in the area, could have a pronounced effect on the redox activity of PM, with broad implications for the protection of public health.
交通是城市的一个重要污染源，在全球范围内引发了各种健康和环境问题。因此，更好地了解交通对颗粒物浓度及其成分的影响有助于减轻空气污染。在本研究中，于2015年至2017年期间，对加拿大多伦多和温哥华交通密集区域的细颗粒物（PM）和粗颗粒物（PM）中的微量元素特征及来源进行了调查。在附近的城市背景站点，同时也采集了24小时综合PM样本。每个近道路站点的PM和PM质量以及一些元素（即铁、钡、铜、锑、锌、铬）均呈现明显增加，这与由再悬浮和/或磨损源导致的交通排放有关。这些微量元素在PM和PM之间呈现出明显的分配趋势，从而反映了其中一些元素的来源。将正定矩阵因子分解法（PMF）应用于细颗粒物和粗颗粒物金属数据的合并数据（共86种），每个站点有24次观测，以确定不同来源对细颗粒物和粗颗粒物中总金属浓度的贡献。PMF模型识别出四个主要来源，包括两个交通非尾气排放源（地壳/道路扬尘、刹车/轮胎磨损）以及区域和本地工业源。源解析表明，再悬浮的地壳/道路扬尘因子是车辆尾气排放和与交通相关的非尾气排放过程中沉积在地表的总粗颗粒物结合微量元素（即铁、钛、钡、铜、锌、锑、铬）浓度的主要贡献者。与刹车/轮胎磨损相关的第二个非尾气排放因子在两个近道路站点的细颗粒物和粗颗粒物元素（即钡、铁、铜、锌、锑）质量中占相当大的比例。区域和本地工业主要对细颗粒物元素（即硫、砷、硒、镉、铅）浓度有贡献。总体而言，结果表明与交通非尾气排放相关的过程是两个PM组分中各种氧化还原活性金属物种（即铁、铜）的主要贡献者。此外，PM中相当一部分这些金属是水溶性的，这是活性氧物种形成的重要贡献者，因此可能导致对人体细胞的氧化损伤。在该区域不存在大量点源的情况下，控制与交通非尾气排放相关的金属排放似乎可能对PM的氧化还原活性产生显著影响，这对保护公众健康具有广泛意义。
