Browsing by Author "Chen, Hong-Dar"

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Chemical Mass Closure and Chemical Characteristics of Ambient Ultrafine Particles and other PM Fractions
(2010)
Chen, Sheng-Chieh
;
Tsai, Chuen-Jinn
;
Huang, Cheng-Yu
;
Chen, Hong-Dar
;
Chen, Shui-Jen
Ambient ultrafine particles (UPs or PM(0.1)), PM(2.5) and PM(10) were investigated at the roadside of Syuefu road in Hsinchu city and in the Syueshan highway tunnel in Taipei, Taiwan. A SMPS (TSI Model 3936), three Dichotomous samplers (Andersen Model SA-241), and three MOUDIs (MSP Model 110) were collocated to determine the PM number and mass concentrations simultaneously. The filter samples were further analyzed for organic carbon (OC), element carbon (EC), water-soluble ions, and trace elements. The OC artifact was studied and quantified using the quartz behind quartz (QBQ) method for all PM fractions. Taking into account the OC artifact, chemical mass closure (ratio of the reconstructed chemical mass to the gravimetrical mass) of PM(0.1), PM(2.5), and PM(10) was then calculated and found to be good. The chemical analysis results of UPs at both sites showed that UPs in the present tunnel was mostly contributed from the vehicle emissions while UPs at the roadside was mainly influenced by urban sources.
The Influence of Relative Humidity on Nanoparticle Concentration and Particle Mass Distribution Measurements by the MOUDI
(2011)
Chen, Sheng-Chieh
;
Tsai, Chuen-Jinn
;
Chen, Hong-Dar
;
Huang, Cheng-Yu
;
Roam, Gwo-Dong
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 PM(0.1) 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 mu m in aerodynamic diameter severely. Oversampling of PM(0.1) 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 PM(0.1) and PM(2.5) 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.