Mitigation of PAH and Nitro-PAH Emissions from Nonroad Diesel Engines

More stringent emission requirements for nonroad diesel engines introduced with U.S. Tier 4 Final and Euro Stage IV and V regulations have spurred the development of exhaust aftertreatment technologies. In this study, several aftertreatment configurations consisting of diesel oxidation catalysts (DO...

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Bibliographic Details
Published in:Environmental science & technology 2015-03, Vol.49 (6), p.3662-3671
Main Authors: Liu, Z. Gerald, Wall, John C, Ottinger, Nathan A, McGuffin, Dana
Format: Article
Language:English
Subjects:
Air Pollutants - analysis
Air Pollution - prevention & control
Ammonia
Automobiles
California
Catalysis
Diesel engines
Emission standards
Emissions
Gasoline
Hydrocarbons
Nitrosation
Oxidation
Polycyclic aromatic hydrocarbons
Polycyclic Aromatic Hydrocarbons - analysis
Toxicity
United States
United States Environmental Protection Agency
Vehicle Emissions - analysis
Vehicle Emissions - prevention & control
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Summary:More stringent emission requirements for nonroad diesel engines introduced with U.S. Tier 4 Final and Euro Stage IV and V regulations have spurred the development of exhaust aftertreatment technologies. In this study, several aftertreatment configurations consisting of diesel oxidation catalysts (DOC), diesel particulate filters (DPF), Cu zeolite-, and vanadium-based selective catalytic reduction (SCR) catalysts, and ammonia oxidation (AMOX) catalysts are evaluated using both Nonroad Transient (NRTC) and Steady (8-mode NRSC) Cycles in order to understand both component and system-level effects of diesel aftertreatment on emissions of polycyclic aromatic hydrocarbons (PAH) and their nitrated derivatives (nitro-PAH). Emissions are reported for four configurations including engine-out, DOC+CuZ-SCR+AMOX, V-SCR+AMOX, and DOC+DPF+CuZ-SCR+AMOX. Mechanisms responsible for the reduction, and, in some cases, the formation of PAH and nitro-PAH compounds are discussed in detail, and suggestions are provided to minimize the formation of nitro-PAH compounds through aftertreatment design optimizations. Potency equivalency factors (PEFs) developed by the California Environmental Protection Agency are then applied to determine the impact of aftertreatment on PAH-derived exhaust toxicity. Finally, a comprehensive set of exhaust emissions including criteria pollutants, NO2, total hydrocarbons (THC), n-alkanes, branched alkanes, saturated cycloalkanes, aromatics, aldehydes, hopanes and steranes, and metals is provided, and the overall efficacy of the aftertreatment configurations is described. This detailed summary of emissions from a current nonroad diesel engine equipped with advanced aftertreatment can be used to more accurately model the impact of anthropogenic emissions on the atmosphere.
ISSN:0013-936X
1520-5851
DOI:10.1021/es505434r