Abstract
A super-sonic impactor using a Laval nozzle, which has been developed for size and concentration controls of ultra-fine aerosol particles down to nano-size range, was applied for the high speed sampling of ultra-fine ambient aerosol. The larger amount of ultra-fine ambient aerosol sampled in short period using the super-sonic impactor is expected to provide more detailed information of chemical components with the higher time resolution. Ambient aerosol (PM) were classified into two different size classes, or <100-200nm and above by the super-sonic impactor. Chemical components such as carbons(total carbon(TC)/elemental carbon(EC)/organic carbon(OC)), polycyclic aromatic hydrocarbons (PAHs), water solubles were analyzed. Concentration and chemical components of sampled particles were compared with those of total suspended particulates in order to evaluate wall loss and evaporation loss and artifacts due to the super-saturation of water vapor in the supersonic flow. Influence of air humidity, which may lead to the generation of water droplet, was also investigated using a diffusion dryer. Ambient particles were confirmed to be separated around 100-200nm using the supersonic impactor. When the humid air was sampled, concentration of particles collected on the backup filter downstream the supersonic impactor decreased probably because of the condensation of water vapor. There may be a possibility of an increase in collected amount of semi-volatile compounds to the backup filter due to the influence of super-saturation.
