Abstract
The evaluation of collection efficiencies of aerosol samplers becomes challenging with high pressure drops. The evaluation approaches applied at various conditions deserve further development, especially when a high pressure drop is induced by the sampler. In this work, an elution-based method using NaCl aerosol was proposed to estimate the size-resolved collection efficiency which was not affected by the pressure drop. More specifically, a Condensation Particle Counter (CPC) was used to count the upstream particle number, and the collected NaCl particles were eluted and determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for estimating the collected particle number. The relationship between number-based concentration and mass-based concentration of NaCl particles was established. A stainless steel impactor for Differential Mobility Analyzer (DMA), polydimethylsiloxane (PDMS)-based microchannel, and a homemade impactor containing 151 nozzles with a diameter of 0.1 mm were employed to investigate the feasibility of the elution method. DMA-selected particles with a nominal size are considered to be the monodisperse aerosol, which was commonly used for estimating the collection efficiencies of samplers, but size redistribution of downstream monodisperse aerosol with the particle size smaller than 100 nm and larger than the cutoff size (D50) was revealed through the elution method, which affected the collection efficiency measured by either conventional CPC- or elution-based method. It was found that the elution method was dependent on the D50 value of the sampler, and the applicable size range was from 100 nm to D50 (D50 < 500 nm) or from 100 nm to 500 nm (D50 greater than 500 nm). This study provided insights into the size-dependent particle transport through aerosol samplers, and the development of an elution-based method to estimate pressure drop-independent collection efficiencies.
Highlights
Aerosol samplers such as impactors, impingers, and cyclones are widely used to collect or classify airborne particles [1]
The elution-based method might be applicable in a wider size range if a more monodisperse NaCl particles could be generated in future studies, especially for particles larger than 500 nm
Size redistribution of monodisperse NaCl particles due to the diffu sion of particles smaller than 100 nm and bouncing of particles larger than D50 or 500 nm were found to affect the estimation of collection efficiency
Summary
Aerosol samplers such as impactors, impingers, and cyclones are widely used to collect or classify airborne particles [1]. To evaluate the aerosol samplers, its size-resolved collection efficiency is normally investigated. Obtaining an accurate particle size and number concen tration becomes challenging when the inlet pressure of the online in struments is outside the operating range due to the high pressure drop induced by samplers [3]. Condensation Particle Counter (CPC) 3775 could operate normally only at an inlet pressure of 0.75 to 1.05 atm [4]. Under a low pressure condition (e.g. 0.5 atm), the counting efficiency of a CPC can be largely reduced due to the particle diffusion
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
