title: Hydrocarbon condensation in heavy-duty diesel exhaust.
abstract: The semivolatile mass fraction of diesel exhaust particles was studied using size-resolved on-line techniques (DMA-ELPI; TDMA-ELPI). The average density of the semivolatile liquid on the particles was measured to be approximately 0.8 g/cm3. The measured size resolved values of mass transfer imply that condensation, or diffusion-limited mass transfer, plays a major role in driving the volatile matter to the diesel exhaust particles. The measured mass change values correspond to highly size dependent mass fractions for the semivolatile component, ranging from approximately 20-80%. Integrated over particle size distribution, the volatile mass fractions were 25 and 45% for the two load points studied. Calculation, based on the measured particle properties, indicates that only 10% volatile mass fraction could be explained by monolayer adsorption. The size resolved changes in particle effective density, fractal dimension, volatile mass fractions and mass are all in agreement with theoretical considerations of condensation.
authors.affiliation: Aerosol Physics Laboratory, Institute of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland, USA.
authors.forename: Jyrki
authors.initials: J
authors.lastname: Ristimäki
authors.forename: Kati
authors.initials: K
authors.lastname: Vaaraslahti
authors.forename: Maija
authors.initials: M
authors.lastname: Lappi
authors.forename: Jorma
authors.initials: J
authors.lastname: Keskinen
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D004784:Environmental Monitoring; D006838:Hydrocarbons / Q000737:chemistry*; D010316:Particle Size; D001335:Vehicle Emissions / Q000032:analysis*; D014835:Volatilization
chemical_list: D000393:Air Pollutants; D006838:Hydrocarbons; D001335:Vehicle Emissions