Secondary effects of catalytic diesel particulate filters: conversion of PAHs versus formation of nitro-PAHs
| Autor: | Jean-Luc Petermann, Erika Gujer, Markus Kasper, Kerstin Zeyer, Markus Zennegg, Peter Schmid, Andrea Ulrich, Lukas Emmenegger, Urs Gfeller, Jan Czerwinski, Adrian Wichser, Andreas Mayer, Martin Kohler, Peter Honegger, Norbert V. Heeb, Daniela Wenger, Thomas Mosimann |
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| Rok vydání: | 2008 |
| Předmět: |
Diesel particulate filter
Diesel exhaust Chemistry Exhaust gas General Chemistry Particulates medicine.disease_cause Diesel engine complex mixtures Soot Catalysis law.invention chemistry.chemical_compound Nitric acid law Catalytic converter medicine Environmental Chemistry Organic chemistry Polycyclic Compounds Vehicle Emissions |
| Zdroj: | Environmental sciencetechnology. 42(10) |
| ISSN: | 0013-936X |
| Popis: | 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 (NO2), nitric acid (HNO3), 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-nitrophenanthrene 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 for1% of the total AHR-mediated response, indicating that considerable amounts of other aryl hydrocarbons must be present in filtered and unfiltered 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. |
| Databáze: | OpenAIRE |
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