Center for Atmospheric Particle Studies and ‡Department of Mechanical Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
Environ Sci Technol. 2015 Oct 6;49(19):11516-26. doi: 10.1021/acs.est.5b02841. Epub 2015 Sep 14.
Emissions of intermediate-volatility organic compounds (IVOCs) from five on-road diesel vehicles and one off-road diesel engine were characterized during dynamometer testing. The testing evaluated the effects of driving cycles, fuel composition and exhaust aftertreatment devices. On average, more than 90% of the IVOC emissions were not identified on a molecular basis, instead appearing as an unresolved complex mixture (UCM) during gas-chromatography mass-spectrometry analysis. Fuel-based emissions factors (EFs) of total IVOCs (speciated + unspeciated) depend strongly on aftertreatment technology and driving cycle. Total-IVOC emissions from vehicles equipped with catalyzed diesel particulate filters (DPF) are substantially lower (factor of 7 to 28, depending on driving cycle) than from vehicles without any exhaust aftertreatment. Total-IVOC emissions from creep and idle operations are substantially higher than emissions from high-speed operations. Although the magnitude of the total-IVOC emissions can vary widely, there is little variation in the IVOC composition across the set of tests. The new emissions data are combined with published yield data to investigate secondary organic aerosol (SOA) formation. SOA production from unspeciated IVOCs is estimated using surrogate compounds, which are assigned based on gas-chromatograph retention time and mass spectral signature of the IVOC UCM. IVOCs contribute the vast majority of the SOA formed from exhaust from on-road diesel vehicles. The estimated SOA production is greater than predictions by previous studies and substantially higher than primary organic aerosol. Catalyzed DPFs substantially reduce SOA formation potential of diesel exhaust, except at low speed operations.
在测功机测试期间，对五辆道路柴油车和一台非道路柴油发动机排放的中等挥发性有机化合物（IVOC）进行了特征描述。该测试评估了驾驶循环、燃料成分和废气后处理装置的影响。平均而言，超过 90%的 IVOC 排放物无法从分子基础上确定，而是在气相色谱-质谱分析中表现为未解析复杂混合物（UCM）。基于燃料的总 IVOC（有谱和无谱）排放因子（EF）强烈依赖于后处理技术和驾驶循环。装有催化柴油颗粒过滤器（DPF）的车辆的总-IVOC 排放量大大降低（取决于驾驶循环，因子为 7 至 28），而没有任何废气后处理的车辆的排放量则大大降低。蠕行和怠速操作的总-IVOC 排放量明显高于高速操作的排放量。尽管总-IVOC 排放量的幅度可能变化很大，但在一系列测试中，IVOC 组成的变化很小。新的排放数据与已发表的产率数据结合起来，用于研究二次有机气溶胶（SOA）的形成。使用替代化合物来估计未解析的 IVOC 的 SOA 生成量，这些替代化合物是根据气相色谱保留时间和 IVOC UCM 的质谱特征分配的。IVOC 对道路柴油车尾气形成的 SOA 贡献了绝大部分。估计的 SOA 生成量大于先前研究的预测值，并且大大高于初级有机气溶胶。除了在低速运行时，催化 DPF 大大降低了柴油废气的 SOA 形成潜力。
