title: Effect of advanced aftertreatment for PM and NOx reduction on heavy-duty diesel engine ultrafine particle emissions.
abstract: Four heavy-duty and medium-duty diesel vehicles were tested in six different aftertreament configurations using a chassis dynamometer to characterize the occurrence of nucleation (the conversion of exhaust gases to particles upon dilution). The aftertreatment included four different diesel particulate filters and two selective catalytic reduction (SCR) devices. All DPFs reduced the emissions of solid particles by several orders of magnitude, but in certain cases the occurrence of a volatile nucleation mode could increase total particle number emissions. The occurrence of a nucleation mode could be predicted based on the level of catalyst in the aftertreatment, the prevailing temperature in the aftertreatment, and the age of the aftertreatment. The particles measured during nucleation had a high fraction of sulfate, up to 62% of reconstructed mass. Additionally the catalyst reduced the toxicity measured in chemical and cellular assays suggesting a pathway for an inverse correlation between particle number and toxicity. The results have implications for exposure to and toxicity of diesel PM.
authors.affiliation: California Air Resources Board, 1001 I Street, PO Box 2815, Sacramento, California 95812, United States. jherner@arb.ca.gov
authors.forename: Jorn Dinh
authors.initials: JD
authors.lastname: Herner
authors.forename: Shaohua
authors.initials: S
authors.lastname: Hu
authors.forename: William H
authors.initials: WH
authors.lastname: Robertson
authors.forename: Tao
authors.initials: T
authors.lastname: Huai
authors.forename: M-C Oliver
authors.initials: MC
authors.lastname: Chang
authors.forename: Paul
authors.initials: P
authors.lastname: Rieger
authors.forename: Alberto
authors.initials: A
authors.lastname: Ayala
mesh_terms: D000397:Air Pollution / Q000517:prevention & control; D001336:Automobiles / Q000706:statistics & numerical data*; D003247:Conservation of Natural Resources / Q000379:methods; D005374:Filtration; D009589:Nitrogen Oxides / Q000032:analysis / Q000737:chemistry*; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis / Q000737:chemistry*; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D009589:Nitrogen Oxides; D052638:Particulate Matter; D001335:Vehicle Emissions