Formation of Nitrated Polycyclic Aromatic Hydrocarbons (NPAHs) in Combustion Engine Exhaust Studied by Laser Photofragmentation

通过激光光碎裂研究内燃机排气中硝化多环芳烃 (NPAH) 的形成

• 批准号: 248993947
• 负责人: Professor Dr. Christoph Haisch
• 金额: --
• 依托单位: Lehrstuhl für Analytische Chemie und Wasserchemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/248993947?language=en
• 关键词: Formation; Nitrated; Polycyclic; Aromatic; Hydrocarbons

Nitrated Polycyclic Aromatic Hydrocarbons (NPAHs), together with its parent compound PAHs, are probably the abiotic class of substances which is most harmful for human health. A large part, more than one third of the mutagen potential of ambient air is attributable to NPAHs. NPAHs are formed during combustion in the presence of NO2. NPAHs in combustion engine exhaust are particularly hazardous due to their attachment to soot particles, which act as transport vehicles across the alveolar membrane into the organism and across walls of red blood cells. Some strategies used in Diesel particulate filters (DPF) make use of excess NO2. This led to intense discussions about possible de-novo formation of NPAHs within an exhaust aftertreatment system. However, compared to other air pollutants, knowledge of occurrence, formation, and sinks is much more fragmentary and incomplete. The reason for this gap is semivolatility, instability, and lack of sensitivity of existing measuring techniques. For more than two decades, no major progress was achieved with regard to most of these aspects. In exhaust gas, filter-based sampling and subsequent analysis is particularly prone to artifact formation. Here, we propose to advance knowledge of NPAHs by (1) providing a fast, artifact-free measurement method for NPAHs and PAHs, which will allow to (2) study NPAH formation, degradation and sorption of NPAH from PAH on aerosol particulate matter under controlled conditions in a flow reactor, simulating an automotive exhaust system, (3) direct, artifact-free study of NPAHs and PAHs on the exhaust system of a combustion engine. This demanding challenge will be performed laser-photofragmentation (PF). PF is the selective fragmentation of a chemical bond by light. Selectivity is defined by the selected wavelength, corresponding to a specific photon energy, which is equal to the chemical binding energy. The generated fragments, in our case of NPAH detection, the nitro group and the remaining PAH, will be detected either by their optical emission, when the fragments are generated in the excited state, or by the current due to fragment ions. Although the fundamentals of PF are known for decades, we believe that by novel instrumentation, this techniques can successfully be implemented for the routine application of the challenging task of a highly sensitive on-line NPAH detection.

硝化多环芳烃（NPAHs）及其母体化合物多环芳烃（PAHs）可能是对人类健康危害最大的一类非生物物质。环境空气中有三分之一以上的潜在诱变剂是由NPAH引起的。NPAH是在燃烧过程中在NO2的存在下形成的。内燃机废气中的NPAH特别危险，因为它们附着在烟尘颗粒上，烟尘颗粒作为运输工具穿过肺泡膜进入生物体并穿过红细胞壁。柴油机微粒过滤器（DPF）中使用的一些策略利用过量的NO2。这导致了关于排气后处理系统内可能重新形成NPAH的激烈讨论。然而，与其他空气污染物相比，关于发生、形成和汇的知识更加零碎和不完整。造成这一差距的原因是半波动性、不稳定性和现有测量技术缺乏灵敏度。20多年来，在这些方面的大多数方面都没有取得重大进展。在废气中，基于过滤器的采样和后续分析特别容易形成伪影。在这里，我们建议通过（1）提供一种快速、无人为因素的NPAH和PAH测量方法来提高对NPAH的认识，这将允许（2）在流动反应器中模拟汽车排气系统，在受控条件下研究NPAH的形成、降解和NPAH在气溶胶颗粒物上的吸附，（3）直接，NPAH和PAH对内燃机排气系统的无人为影响研究。这一艰巨的挑战将通过激光光致碎裂（PF）来完成。PF是光对化学键的选择性断裂。选择性由所选择的波长定义，对应于特定的光子能量，其等于化学结合能。所产生的碎片，在我们的NPAH检测的情况下，硝基和剩余的PAH，将通过它们的光发射（当碎片在激发态下产生时）或通过由于碎片离子产生的电流来检测。虽然PF的基本原理是已知的几十年，我们相信，通过新的仪器，这种技术可以成功地实现一个高度敏感的在线NPAH检测的挑战性任务的常规应用。