Center for Atmospheric and Cloud Chemistry, Aerodyne Research, Inc., Billerica, MA 01983, USA.
J Air Waste Manag Assoc. 2010 Oct;60(10):1192-203. doi: 10.3155/1047-3289.60.10.1192.
Aerosol mass spectrometer (AMS) measurements are used to characterize the evolution of exhaust particulate matter (PM) properties near and downwind of vehicle sources. The AMS provides time-resolved chemically speciated mass loadings and mass-weighted size distributions of nonrefractory PM smaller than 1 microm (NRPM1). Source measurements of aircraft PM show that black carbon particles inhibit nucleation by serving as condensation sinks for the volatile and semi-volatile exhaust gases. Real-world source measurements of ground vehicle PM are obtained by deploying an AMS aboard a mobile laboratory. Characteristic features of the exhaust PM chemical composition and size distribution are discussed. PM mass and number concentrations are used with above-background gas-phase carbon dioxide (CO2) concentrations to calculate on-road emission factors for individual vehicles. Highly variable ratios between particle number and mass concentrations are observed for individual vehicles. NRPM1 mass emission factors measured for on-road diesel vehicles are approximately 50% lower than those from dynamometer studies. Factor analysis of AMS data (FA-AMS) is applied for the first time to map variations in exhaust PM mass downwind of a highway. In this study, above-background vehicle PM concentrations are highest close to the highway and decrease by a factor of 2 by 200 m away from the highway. Comparison with the gas-phase CO2 concentrations indicates that these vehicle PM mass gradients are largely driven by dilution. Secondary aerosol species do not show a similar gradient in absolute mass concentrations; thus, their relative contribution to total ambient PM mass concentrations increases as a function of distance from the highway. FA-AMS of single particle and ensemble data at an urban receptor site shows that condensation of these secondary aerosol species onto vehicle exhaust particles results in spatial and temporal evolution of the size and composition of vehicle exhaust PM on urban and regional scales.
气溶胶质谱仪 (AMS) 测量用于描述车辆源附近和下风处排放颗粒物 (PM) 特性的演变。AMS 提供了非难处理性 PM1 小于 1 微米 (NRPM1) 的时间分辨化学特征质量负荷和质量加权粒径分布。飞机 PM 的源测量表明，黑碳颗粒作为挥发性和半挥发性排气的冷凝阱，抑制了成核。通过在移动实验室中部署 AMS，获得了地面车辆 PM 的实际源测量。讨论了排气 PM 化学成分和粒径分布的特征。使用 PM 质量和数量浓度以及背景以上的气相二氧化碳 (CO2) 浓度，计算了个别车辆的道路排放因子。个别车辆的颗粒数浓度与质量浓度之间的比值变化很大。在道路上测量的柴油车的 NRPM1 质量排放因子比测功机研究低约 50%。首次将 AMS 数据的因子分析 (FA-AMS) 应用于映射高速公路下风处排气 PM 质量的变化。在这项研究中，靠近高速公路的车辆 PM 浓度高于背景，远离高速公路 200 米处的浓度降低了 2 倍。与气相 CO2 浓度的比较表明，这些车辆 PM 质量梯度主要是由稀释引起的。二次气溶胶物种的绝对质量浓度没有表现出类似的梯度；因此，它们对总环境 PM 质量浓度的相对贡献随着与高速公路的距离的增加而增加。在城市受体点的单颗粒和整体数据的 FA-AMS 表明，这些二次气溶胶物种在车辆排气颗粒上的凝结导致车辆排气 PM 的大小和组成在城市和区域尺度上的时空演变。
