School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
State Environmental Protection Key Laboratory of the Cause and Prevention of Urban Air Pollution Complex, Shanghai Academy of Environmental Sciences, Shanghai, 200233, China.
Environ Pollut. 2021 Jul 15;281:117020. doi: 10.1016/j.envpol.2021.117020. Epub 2021 Mar 25.
Intermediate-volatility organic compounds (IVOCs) emitted from vehicles are generally in the gas phase but may partly partition into particle phase when measured under ambient temperature. To have a complete and accurate picture of IVOC emissions from vehicles, gas- and particle-phase IVOCs from a fleet of gasoline and diesel vehicles were simultaneously characterized by dynamometer testing in Guangzhou, China. The total IVOC emission factors of the diesel vehicles were approximately 16 times those of the gasoline vehicles, and IVOCs were mainly concentrated in the particle phase in the form of the unresolved complex mixture (UCM). The chemical compositions and volatility distributions of the gas-phase IVOCs differed much between gasoline and diesel vehicles, but were similar to those of their respective fuel content. This indicated that vehicle fuel is the main origin for the gas-phase IVOC emissions from vehicles. In comparison, the chemical compositions of the particle-phase IVOCs from gasoline and diesel vehicles were similar and close to lubricating oil content, implying that lubricating oil plays an important role in contributing to particle-phase IVOCs. The highest IVOC fraction in the particle phase occurred from B-B volatility bins, overall accounting for more than half of the particle-phase IVOCs for both the gasoline and diesel vehicles. A conceptual model was developed to articulate the distributions of lubricating oil contents and their evaporation and nucleation/adsorption capabilities in the different volatility bins. The IVOCs-produced secondary organic aerosol (SOA) were 1.4-2.6 and 3.9-11.7 times POAs emitted from the gasoline and diesel vehicles, respectively. The tightening of emission standards had not effectively reduced IVOC emissions and the SOA production until the implementation of China VI emission standard. This underscores the importance of accelerating the promotion of the latest emission standard to alleviate pollution from vehicles in China.
车辆排放的中等挥发性有机化合物（IVOCs）通常处于气相，但在环境温度下测量时可能部分分配到颗粒相中。为了全面准确地了解车辆排放的 IVOC，我们通过在中国广州的测功机测试对汽油和柴油车辆车队的气相和颗粒相 IVOC 进行了同时表征。柴油车辆的总 IVOC 排放因子约为汽油车辆的 16 倍，IVOC 主要以未解析复杂混合物（UCM）的形式集中在颗粒相中。汽油和柴油车辆的气相 IVOC 的化学成分和挥发性分布有很大差异，但与各自的燃料含量相似。这表明车辆燃料是车辆气相 IVOC 排放的主要来源。相比之下，汽油和柴油车辆的颗粒相 IVOC 的化学成分相似，接近润滑油含量，这意味着润滑油在颗粒相 IVOC 贡献中起着重要作用。颗粒相 IVOC 中最高的 IVOC 分数出现在 B-B 挥发性箱中，总体占汽油和柴油车辆颗粒相 IVOC 的一半以上。我们建立了一个概念模型来阐述不同挥发性箱中润滑油含量及其蒸发和成核/吸附能力的分布。IVOC 产生的二次有机气溶胶（SOA）分别是汽油和柴油车辆颗粒有机气溶胶（POA）的 1.4-2.6 倍和 3.9-11.7 倍。直到实施中国 VI 排放标准，排放标准的收紧才有效地减少了 IVOC 排放和 SOA 生成。这突显了加速推广最新排放标准以减轻中国车辆污染的重要性。
