The influence of relative humidity on nanoparticle concentration and particle mass distribution measurements by the MOUDI

Sheng Chieh Chen, Chuen-Tinn Tsai*, Hong Dar Chen, Cheng Yu Huang, Gwo Dong Roam

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

A humidity control system was operated upstream of two collocated MOUDIs (micro-orifice uniform deposit impactors) for sampling ambient aerosol particles. One MOUDI used silicone-grease-coated aluminum foils (ALs) as the impaction substrates and was considered as the reference impactor, while the other used uncoated ALs or uncoated Teflon filters (TFs) as the impaction substrates for quantifying the effect of different relative humidities (RHs) and impaction substrates on the PM0.1 concentrations and mass distributions of ambient PMs. Test results showed that decreasing RH in general increased particle bounce from uncoated substrates with the bounce from uncoated ALs being more severe than that from uncoated TFs. Particle bounce did not influence the overall mass distribution of ambient fine particles when RH ranged between 40% and 80%, whereas it led to undersampling of particles greater than 2.5 μm in aerodynamic diameter severely. Oversampling of PM0.1 occurred by as much as 95%-180% or 25%-55% when the MOUDI used uncoated ALs or TFs, respectively, as RH was reduced from 50% to 25%. Particle bounce was found to be negligible, and PM0.1 and PM2.5 could be sampled accurately with less than 5% error at the RH of 75%-80% or 65%-80% when uncoated ALs or TFs were used, respectively.

Original languageEnglish
Pages (from-to)596-603
Number of pages8
JournalAerosol Science and Technology
Volume45
Issue number5
DOIs
StatePublished - 1 May 2011

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