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首页> 外文会议>ACS Symposium Series 890; Symposium on Nanotechnology and the Environment: Applications and Implications; ; >Single-Particle Mass Spectrometry of Metal-Bearing Diesel Nanoparticles
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Single-Particle Mass Spectrometry of Metal-Bearing Diesel Nanoparticles

机译：含金属的柴油纳米颗粒的单颗粒质谱

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It is known that diesel engines produce a tri-modal size distribution of DPM (diesel particulate matter), (1). The number of nano-size particles i.e. those in the "nuclei" mode, is quite variable and can be attributed in many cases to the self-nucleation of volatile species during the dilution and simultaneous cooling of the exhaust. In some cases nanoparticles may also form prior to dilution (2, 3). The dynamics of particle formation during and after combustion is a topic of much interest and investigation. A recent summary of the diesel combustion process (4) describes how the fuel jet quickly disintegrates as it exits the nozzle and vaporizes as it entrains hot air, subsequently forming a teardrop-shaped cloud of fuel-vapor and air mixture with a diffusion flame at its periphery. Particles of soot originate from pyrolysis of fuel in the fuel-rich region of this diffusion flame. These primary soot particles are spherical and consist of many layers of carbon atoms and/or multi-atom platelets. As the piston moves downward, rapid adiabatic cooling causes these primary particles to agglomerate. At this stage, if there are any species (such as metals) with very high concentrations, they may self-nucleate if the rapid cooling drives their saturation ratios high enough. As the resulting aerosol travels through the exhaust system, further cooling causes condensation of other species onto the . particles. When the aerosol exits the tailpipe it again cools rapidly and other more volatile species condense suddenly and/or self-nucleate into nanoparticles. The resulting mixture of gases and particles is what we call DPM. Both acute and chronic health effects have been associated with DPM. One theory holds that the potentially large number of ultrafine particles and their characteristic high lung-penetration efficiency may play a role in this correlation (5), and it is also possible that the presence of metals may be a contributor. To address these issues, the UMN and NIOSH are conducting a joint investigation to characterize the metal content of diesel nanoparticles and this report summarizes preliminary findings. The research aims at providing insight into the formation of metal-rich nanoparticles via self-nucleation as well as the overall distribution of metal across a wider range of particle sizes due to condensation and coagulation.
机译：众所周知，柴油发动机会产生DPM（柴油颗粒物）的三峰尺寸分布（1）。纳米尺寸的颗粒，即处于“核”模式的颗粒的数量是可变的，并且在许多情况下可归因于在稀释和同时冷却排气时挥发性物质的自成核。在某些情况下，也可以在稀释之前形成纳米颗粒（2、3）。燃烧期间和之后的颗粒形成动力学是一个非常令人感兴趣和研究的话题。柴油机燃烧过程（4）的最新摘要描述了燃料喷射流如何在离开喷嘴时迅速分解并在夹带热空气时蒸发，随后形成泪珠状的燃料-蒸气和空气混合物云，并在火焰处扩散它的外围。烟尘颗粒源自该扩散火焰的燃料富集区域中的燃料热解。这些初级烟灰颗粒是球形的，并且由许多碳原子层和/或多原子血小板组成。当活塞向下移动时，快速的绝热冷却导致这些初级粒子凝聚。在此阶段，如果存在任何浓度很高的物质（例如金属），则在快速冷却将其饱和比提高到足够高的情况下，它们可能会自成核。当产生的气溶胶穿过排气系统时，进一步的冷却导致其他物质凝结在空气中。粒子。当气雾剂从排气管排出时，它再次迅速冷却，其他易挥发的物质突然凝结和/或自成核形成纳米颗粒。产生的气体和颗粒混合物就是我们所说的DPM。急性和慢性健康影响均与DPM相关。一种理论认为，潜在的大量超细颗粒及其特征性的高肺穿透效率可能在这种相关性中起作用（5），并且金属的存在也可能是一个原因。为了解决这些问题，UMN和NIOSH正在进行联合调查，以表征柴油纳米颗粒的金属含量，本报告总结了初步发现。这项研究旨在通过自成核提供富金属纳米颗粒形成的信息，以及由于凝结和凝结而在更宽的粒径范围内金属的整体分布。

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