Size Distributions of Polycyclic Aromatic Hydrocarbons in Diesel Exhaust Particles Collected by Newly Developed Ultrafine Particles Sampler

摘要

A new type ultrafine particles (< 0.1 μm) sampler called Nanosampler was developed for sizeclassified sampling of atmospheric particles. The sampler can operate at atmospheric pressure under low pressure drop and high sampling flow rate. Six stages can classify particles from less than 0.1 μm to more than 10 μm. In this study, the size distributions of diesel exhaust particles (DEP) were compared with two types of sampler, Nanosampler and Electrical Low Pressure Impactor (ELPI). In addition, total DEP masses were compared with three types of sampler, Nanosampler, conventional filter sampler for DEP and ELPI. DEP was collected from 3-L diesel engine equipped with and without diesel particulate filter (DPF). The results showed the size distributions of DEP without DPF were unimodal with peak at less than 0.1 μm and at 0.11- 0.17 μm by Nanosampler and ELPI, respectively. DEP mass of ultrafine particles fraction by Nanosampler was higher than ELPI. Total DEP masses by ELPI were higher than Nanosampler and conventional filter sampler because the density used in the calculating the mass might be difference from a true value. Polycyclic aromatic hydrocarbons (PAHs) in collected DEP using Nanosampler were analyzed by thermal desorption gas chromatography-mass spectrometer (TDGC- MS). PAHs had clearly unimodal with peak at 0.1 - 0.5 μm under low load (75 Nm) without DPF. When middle load condition, PAHs emission was so small that peak was not clearly. Consequently, Nanosampler was useful to investigate chemical composition of ultrafine particles fraction in DEP.