University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, USA.
American University of Beirut, Department of Chemistry, Beirut, Lebanon.
Sci Total Environ. 2014 Feb 1;470-471:417-26. doi: 10.1016/j.scitotenv.2013.09.104. Epub 2013 Oct 22.
To assess particle oxidative potential in the greater Beirut area, size-resolved PM10-2.5, PM2.5-0.25 and PM0.25 samples were collected at near-freeway and urban background sites. Metals and trace elements, including Mn, Cr, Cu, Ba, Mo and Sb, displayed increased levels and crustal enrichment factors at the roadway, indicating their vehicular origin. These elements in addition to Co, V, Ni and Zn were mostly distributed in PM2.5-0.25 and PM0.25 at both sites, with moderate-to-high water-solubility (>30%). The presence of these metals, mainly air toxics, in small size ranges constitutes an added health risk. Of particular concern are elements with strong correlations (R ≥ 0.70) with reactive oxygen species (ROS)-activity, measured by a cellular assay. In PM10-2.5, road dust component Mn and soil-related element Co were highly correlated with ROS-activity. In PM2.5-0.25, vehicular abrasion element Cu and soil-derived component Co were highly associated with ROS-activity. In PM0.25, V and Ni, originating from fuel oil combustion, strongly correlated with ROS formation. ROS-activity displayed a particle-size dependency, with lowest activity associated with PM10-2.5. On a per air volume basis, size-resolved ROS-activity was 1.5-2.8 times greater at the roadside than background location, indicating that exposure to redox-active species may be greatest near the freeway. Size-fractionated PM intrinsic activity (i.e. PM mass-normalized) was comparable at both sites, possibly suggesting a similarity in the sources of ROS-active species. Relative to other urban settings, while the intrinsic redox activity of PM10-2.5 in Beirut is comparable to that measured at an urban site in Los Angeles (LA), its PM0.25-induced ROS-activity is ~2.3-fold greater. Moreover, the intrinsic ROS-activity of ambient PM2.5 in Beirut is comparable to that reported in Milan-Italy, but 3.1-times PM2.5 activity in the heavily-polluted Lahore-Pakistan. Lastly, findings suggest a dominant role of transition metals in generating ROS compared to organic carbon in the LA area.
为了评估贝鲁特地区的颗粒氧化势，在高速公路附近和城市背景地区采集了按粒径大小划分的 PM10-2.5、PM2.5-0.25 和 PM0.25 样本。在道路上，金属和微量元素（包括 Mn、Cr、Cu、Ba、Mo 和 Sb）的水平升高，且具有地壳富集因子，表明它们源自车辆。这些元素以及 Co、V、Ni 和 Zn 主要分布在两个地点的 PM2.5-0.25 和 PM0.25 中，水溶性中等至较高（>30%）。这些金属主要是空气毒素，分布在小粒径范围内，构成了额外的健康风险。特别值得关注的是与细胞测定法测量的活性氧物质（ROS）活性呈强相关性（R≥0.70）的元素。在 PM10-2.5 中，道路灰尘成分 Mn 和与土壤有关的元素 Co 与 ROS 活性高度相关。在 PM2.5-0.25 中，车辆磨损元素 Cu 和源自土壤的元素 Co 与 ROS 活性密切相关。在 PM0.25 中，源自燃油燃烧的 V 和 Ni 与 ROS 形成强烈相关。ROS 活性与粒径有关，与 PM10-2.5 相关的活性最低。基于空气体积，在路边的大小分辨 ROS 活性比背景位置高 1.5-2.8 倍，这表明暴露于氧化还原活性物质的风险可能在高速公路附近最大。按 PM 质量归一化，大小分馏的 PM 固有活性在两个地点相似，这可能表明 ROS 活性物质的来源相似。与其他城市环境相比，尽管贝鲁特 PM10-2.5 的固有氧化还原活性与洛杉矶（LA）城市环境中的测量值相当，但 PM0.25 引起的 ROS 活性高约 2.3 倍。此外，贝鲁特环境 PM2.5 的固有 ROS 活性与意大利米兰相当，但在污染严重的巴基斯坦拉合尔的 PM2.5 活性高 3.1 倍。最后，研究结果表明，与洛杉矶地区相比，过渡金属在产生 ROS 方面发挥了主导作用，而不是有机碳。
