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首页> 外文期刊>Environmental Science & Technology >Secondary Effects of Catalytic Diesel Paniculate Filters: Conversion of PAHs versus Formation of Nitro-PAHs
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Secondary Effects of Catalytic Diesel Paniculate Filters: Conversion of PAHs versus Formation of Nitro-PAHs

机译：催化柴油颗粒过滤器的次级作用：多环芳烃的转化与硝基多环芳烃的形成

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Diesel particulate filters (DPFs) are a promising technology to detoxify diesel exhaust. However, the secondary combustion of diesel soot and associated compounds may also induce the formation of new pollutants. Diesel soot is rated as carcinogenic to humans and also acts as a carrier for a variety of genotoxic compounds such as certain polycyclic aromatic hydrocarbons (PAHs) or nitrated PAHs (nitro-PAHs). Furthermore, diesel exhaust contains considerable amounts of nitric oxide (NO), which can be converted to more powerful nitrating species like nitrogen dioxide (NO_2), nitric acid (HNO_3), and others. This mix of compounds may support nitration reactions in DPFs. Herein we report effects of two cordierite-based, monolithic, wall-flow DPFs on emissions of genotoxic PAHs and nitro-PAHs and compare these findings with those of a reporter gene bioassay sensitive to aryl hydrocarbons (AHs). Soot combustion was either catalyzed with an iron- or a copper/iron-based fuel additive (fuel-borne catalysts). A heavy duty diesel engine, operated according to the 8-stage ISO 8178/4 C1 cycle, was used as test platform. Emissions of all investigated 4- to 6-ring PAHs were reduced by about 40-90%, including those rated as carcinogenic. Emissions of 1- and 2-nitronaphthalene increased by about 20-100%. Among the 3-ring nitro-PAHs, emissions of 3-nitrophena'nthrene decreased by about 30%, whereas 9-nitrophenanthrene and 9-nitroanthracene were found only after DPFs. In case of 4-ring nitro-PAHs, emissions of 3-nitrofluoranthene, 1-nitropyrene, and 4-nitropyrene decreased by about 40-60% with DPFs. Total AH-receptor (AHR) agonist concentrations of diesel exhaust were lowered by 80-90%, when using the iron- and copper-based DPFs. The tested PAHs accounted for < 1% of the total AHR-mediated response, indicating that considerable amounts of other aryl hydrocarbons must be present in filtered and unfittered exhaust. We conclude that both DPFs detoxified diesel exhaust with respect to total aryl hydrocarbons, including the investigated carcinogenic PAHs, but we also noticed a secondary formation of selected nitro-PAHs. Nitration reactions were found to be stereoselective with a preferential substitution of hydrogen atoms at peri-positions. The stereoisomers obtained are related to combustion chemistry, but differ from those formed upon atmospheric nitration of PAHs.
机译：柴油机微粒过滤器（DPF）是一种有前途的技术，可以对柴油机废气进行排毒。但是，柴油机烟灰和相关化合物的二次燃烧也可能引起新污染物的形成。柴油烟灰被认为对人类具有致癌性，并且还充当多种遗传毒性化合物的载体，例如某些多环芳烃（PAH）或硝化PAH（硝基-PAH）。此外，柴油机废气中含有大量的一氧化氮（NO），可以将其转化为更强大的硝化物种，例如二氧化氮（NO_2），硝酸（HNO_3）等。化合物的这种混合可以支持DPF中的硝化反应。本文中，我们报告了两种堇青石基整体式壁流DPF对遗传毒性PAHs和硝基PAHs排放的影响，并将这些发现与对芳烃（AHs）敏感的报告基因生物测定法进行了比较。用铁或铜/铁基燃料添加剂（油载催化剂）催化烟尘燃烧。测试平台使用了按照8级ISO 8178/4 C1循环运行的重型柴油发动机。所有调查的4至6环PAH的排放量减少了约40-90％，包括那些被定为致癌的。 1-和2-硝基萘的排放量增加了约20-100％。在3-环硝基-PAHs中，仅在DPF处理后，3-硝基苯并菲的排放量减少了约30％，而9-硝基菲和9-硝基蒽被发现。对于4-环硝基-PAH，使用DPF可使3-硝基荧蒽，1-硝基py和4-硝基py的排放降低约40-60％。使用铁和铜基DPF时，柴油机排气中的总AH受体（AHR）激动剂浓度降低了80-90％。测试的多环芳烃占AHR介导的总响应的<1％，表明在过滤和未过滤的废气中必须存在大量其他芳烃。我们得出的结论是，两种DPF都相对于总芳基烃（包括所研究的致癌PAH）对柴油机废气进行了解毒，但我们还注意到了选定的硝基PAHs的次级形成。发现硝化反应是立体选择性的，在周围位置优先取代了氢原子。所获得的立体异构体与燃烧化学有关，但是不同于在大气中硝化PAHs形成的立体异构体。

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