Development and application of an in-situ measurement system for ultrafine particle effective density

• Main Authors: Pei-Hsuan Chen, 陳珮瑄
• Other Authors: Li-Hao Young
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/q224b8

碩士 === 中國醫藥大學 === 職業安全與衛生學系碩士班 === 102 === Particle effective density (ρeff) contains information on its shape, mobility, aerodynamic and volume equivalent diameters. It therefore could be used to derive ultrafine particle (<100 nm) shape properties, to identify emissions of high-density metal nanoparticles in the workplace, and to convert particle number to particle mass. In addition, conventional methods to derive ρeff such as filter sampling, microscopic and gravimetric analyses have poor time resolution. With that in mind, this study aims to develop an in-situ particle mobility and aerodynamic diameter tandem measurement system to derive highly time-resolved ρeff. The presented aerosol generation system can stably generate different number concentration (102-107 cm-3) of polydisperse or monodisperse particles. With the used of polystyrene latex (PSL) and Faraday cup electrometer (FCE), the collection efficiency curve of the particle aerodynamic size classifier and the calibration of condensation particle counter (CPC) could be determined, respectively. Validation results show that the linear slopes between CPC and FCE were 0.898-0.935 and R2>0.997. For PSL particles, the relative percent difference between the expected and measured da and between the material density (ρm) and measured ρeff were all less than 4 %. For NaCl particles, the measured ρeff were 14 % less that its ρm. Application results show that the ρeff of ultrafine particles in ambient air and scooter engine exhaust had an inverse relationship with db, indicating those particles were more irregular or chain-like with increasing size. For Ag particles, on the other hand, the ρeff were positively correlated with db, though the changes of ρeff were small.