The performance of a newly developed impactor filter sampling system (IF) to classify ultrafine particles (UFP) under atmospheric pressure was evaluated by comparison with a low pressure impactor (LPI) sampler. Tests were carried out in field samplings of atmospheric aerosol. The results showed that the IF is capable of collecting UFP without altering the composition compared to LPI, and the collected amount of OC and EC is 1.4 ∼ 1.6 times higher than LPI sampler. Furthermore, the determination of ionic components like SO42-, NO3- and NH4+, indicated that highly-volatile components are volatilized more significantly when using the LPI sampler. The IF was used to sample PM2.5 and PM0.1 during summer and winter at the roadside of a busy national road. The chemical composition analysis indicated that only PM0.1 had seasonal variation on OC composition, whereas ionic components existed mainly in larger particles. Larger particles seemed to be affected by background particles at the roadside, while PM0.1 were strongly influenced by motor vehicle emissions. Moreover, the relationship between the chemical components in PM0.1 and particle number concentrations confirmed that homogeneous particle growth dominates in summertime, while heterogeneous particle growth dominates in wintertime.
