Abstract
In this study, a homemade steam-based aerosol collector with high time resolution is developed and discussed here in detail. This steam-based aerosol collector can be coupled with water-phase chemical analytical instruments and divided into a few separate parts, including a mixing chamber, steam generator, cooling system, inertial impactor, and vacuum pump. The particulate matter drawn into the system mixes with steam in parallel direction and forms droplets due to the water supersaturation in the mixing chamber. The cooling system maintaining the temperature around 20 °C enhances the steam condensation on the particle surface. In this study, the aerosol collector is operated in the flow rate range from 5.0 to 16.7 L min-1, and the residence time of droplets inside of the mixing chamber is from 1.23 to 4.11 seconds. For evaluating the performance of the collector, the following experiments were conducted. Firstly, the cut size of the inertial impactor was characterized by penetration experiments at 5.0, 10.0, and 16.7 L min-1. The penetration curves with the Stokes number as x-axis can be established to predict the cut size. Secondly, the sizes of particles from 32.2-194.0 nm are enlarged up to the cut size of the inertial impactor at 5.0 to 16.7 L min-1. Thirdly, the particle collection efficiencies were almost 100% at the sizes of test particles from 89.8 to 300.0 nm in 5.0, 10.0, and 16.7 L min-1. Finally, this steam-based aerosol collector with the slit virtual impactor can concentrate the air mass concentration by the inertial motion of particles. The concentrated ratio was around 3 to 4 times based on the experiments.