University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
University of Illinois at Urbana-Champaign, Department of Civil and Environmental Engineering, Urbana-Champaign, IL, USA.
Sci Total Environ. 2018 Jan 1;610-611:1336-1346. doi: 10.1016/j.scitotenv.2017.08.239. Epub 2017 Aug 30.
To investigate the relative impacts of emissions from Los Angeles International Airport (LAX), as well as the impacts of traffic emissions from freeways, on the oxidative potential of particulate matter (PM), PM were collected at two urban background locations in Los Angeles. Redox activity of the PM samples was measured by means of an in vitro alveolar macrophage assay that quantifies the formation of reactive oxygen species (ROS) in cells, and detailed chemical analyses were performed to determine the speciated chemical composition of collected PM. A molecular marker-based chemical mass balance (MM-CMB) model was applied to estimate the relative contributions from the following primary sources to the organic carbon (OC) component of PM: mobile sources (combined gasoline and diesel vehicles), wood smoke, vegetative detritus, road dust and ship emissions. A source profile of aircraft emissions was not included in the model; however its contribution was estimated from un-apportioned primary OC in the MM-CMB model ("other OC") after accounting for the contribution of secondary organic carbon (SOC) to OC. The contribution of mobile sources to OC was 82% and 28% at the central Los Angeles site (freeway emissions) and the LAX site, respectively. The estimated contribution of aircraft emissions to PM OC was 36% at the LAX site. ROS activity levels showed little spatial variability, with no statistically significant difference between the averages observed at LAX (24.75±4.01μgZymosan/m) and central Los Angeles (27.77±2 0.32μgZymosan/m), suggesting similar levels of inhalation exposure to redox active species of PM. A multiple linear regression analysis indicated that the variability in ROS activity is best explained by the chemical markers of major identified sources: EC emitted by traffic, and sulfur, considered in our study as a potential tracer of aircraft emissions, with statistically significantly higher concentrations of sulfur at the LAX site (p<0.001).
为了探究洛杉矶国际机场（LAX）排放物以及高速公路交通排放物对颗粒物（PM）氧化性的相对影响，在洛杉矶的两个城市背景地点采集了 PM 样本。采用体外肺泡巨噬细胞测定法测量 PM 样本的氧化还原活性，该方法定量测定细胞中活性氧（ROS）的形成，并且还进行了详细的化学分析，以确定采集 PM 的化学物质组成。应用基于分子标志物的化学质量平衡（MM-CMB）模型来估计以下主要来源对 PM 中有机碳（OC）成分的相对贡献：移动源（汽油和柴油车的组合）、木烟、植物碎屑、道路灰尘和船舶排放。模型中未包含飞机排放物的源谱；但是，在考虑到二次有机碳（SOC）对 OC 的贡献后，从 MM-CMB 模型中的未分配原始 OC（“其他 OC”）中估计了飞机排放物的贡献。移动源对 OC 的贡献分别为洛杉矶市中心（高速公路排放）和 LAX 站点的 82%和 28%。在 LAX 站点，飞机排放物对 PM OC 的估计贡献为 36%。ROS 活性水平的空间变异性较小，在 LAX（24.75±4.01μgZymosan/m）和洛杉矶市中心（27.77±20.32μgZymosan/m）观测到的平均值之间没有统计学上的显著差异，表明对 PM 中具有氧化还原活性的物质的吸入暴露水平相似。多元线性回归分析表明，ROS 活性的可变性最好由主要识别来源的化学标志物来解释：交通排放的 EC 和硫，在本研究中，硫被认为是飞机排放的潜在示踪剂，在 LAX 站点的硫浓度明显更高（p<0.001）。
