title: Impact of low- and high-oxidation diesel particulate filters on genotoxic exhaust constituents.
abstract: Diesel exhaust contains several genotoxic compounds that may or may not penetrate diesel particulate filters (DPFs). Furthermore, the DPF-supported combustion of soot and adsorbed compounds may lead to the formation of additional pollutants. Herein, we compare the impact of 14 different DPFs on emissions of known genotoxic compounds. During a four year period, these DPFs were tested on a heavy duty diesel engine, operated in the ISO 8178/4 C1 cycle. Integral samples, including gas-phase and particle-bound matter were taken. All DPFs were efficient wall-flow filters with solid particulate number filtration efficiencies eta > 98%. On the basis of their CO, NO, and NO(2) emission characteristics, two different filter families were distinguished. DPFs with high oxidation potential (hox, n = 8) converted CO and NO besides hydrocarbons, whereas low oxidation potential DPFs (lox, n = 6) did not support CO and NO oxidation but still converted hydrocarbons. Lox-DPFs reduced NO(2) from 1.0 +/- 0.3 (engine-out) to 0.42 +/- 0.11 g/kWh (eta = 0.59), whereas hox-DPFs induced a NO(2) formation up to 3.3 +/- 0.7 g/kWh (eta = -2.16). Emissions of genotoxic PAHs decreased for both filter families. Conversion efficiencies varied for individual PAHs and were lower for lox- (eta = 0.31-0.87) than for hox-DPFs (eta = 0.75-0.98). Certain nitro-PAHs were formed indicating that nitration is an important step along PAH oxidation. For example, 1-nitronaphthalene emissions increased from 11 to 17 to 21 microg/L without, with lox-, and hox-DPFs respectively, whereas 2-nitronaphthalene emissions decreased from 25 to 19 to 4.7 microg/L. In contrast to our expectations, the nitration potential of lox-DPFs was higher than the one of hox-DPFs, despite the intense NO(2) formation of the latter. The filters converted most genotoxic PAHs and nitro-PAHs and most soot particles, acting as carriers for these compounds. Hox-DPF exhaust remains oxidizing and therefore is expected to support atmospheric oxidation reactions, whereas lox-DPF exhaust is reducing and consuming oxidants such as ozone, when mixed with ambient air.
authors.affiliation: Swiss Federal Laboratories for Materials Testing and Research, Uberlandstrasse 129, CH-8600 Dubendorf, Switzerland. norbert.heeb@empa.ch
authors.forename: Norbert V
authors.initials: NV
authors.lastname: Heeb
authors.forename: Peter
authors.initials: P
authors.lastname: Schmid
authors.forename: Martin
authors.initials: M
authors.lastname: Kohler
authors.forename: Erika
authors.initials: E
authors.lastname: Gujer
authors.forename: Markus
authors.initials: M
authors.lastname: Zennegg
authors.forename: Daniela
authors.initials: D
authors.lastname: Wenger
authors.forename: Adrian
authors.initials: A
authors.lastname: Wichser
authors.forename: Andrea
authors.initials: A
authors.lastname: Ulrich
authors.forename: Urs
authors.initials: U
authors.lastname: Gfeller
authors.forename: Peter
authors.initials: P
authors.lastname: Honegger
authors.forename: Kerstin
authors.initials: K
authors.lastname: Zeyer
authors.forename: Lukas
authors.initials: L
authors.lastname: Emmenegger
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Petermann
authors.forename: Jan
authors.initials: J
authors.lastname: Czerwinski
authors.forename: Thomas
authors.initials: T
authors.lastname: Mosimann
authors.forename: Markus
authors.initials: M
authors.lastname: Kasper
authors.forename: Andreas
authors.initials: A
authors.lastname: Mayer
mesh_terms: D000393:Air Pollutants / Q000737:chemistry*; D005374:Filtration / Q000295:instrumentation*; D015394:Molecular Structure; D009153:Mutagens / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D009153:Mutagens; D001335:Vehicle Emissions; D010100:Oxygen