Browsing by Author "Tsai, C. -J."

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Characteristics of trace metals in traffic-derived particles in Hsuehshan Tunnel, Taiwan: size distribution, potential source, and fingerprinting metal ratio
(2015-01-01)
Lin, Y. -C.
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Tsai, C. -J.
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Wu, Y. -C.
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Zhang, R.
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Chi, K. -H.
Traffic emissions are a significant source of airborne particulate matter (PM) in ambient environments. These emissions contain an abundance of toxic metals and thus pose adverse effects on human health. Size-fractionated aerosol samples were collected from May to September 2013 by using micro-orifice uniform deposited impactors (MOUDIs). Sample collection was conducted simultaneously at the inlet and outlet sites of Hsuehshan Tunnel in northern Taiwan, which is the second-longest freeway tunnel (12.9 km) in Asia. This endeavor aims to characterize the chemical constituents and size distributions, as well as fingerprinting ratios of particulate metals emitted by vehicle fleets. A total of 36 metals in size-resolved aerosols were determined through inductively coupled plasma mass spectrometry. Three major groups - namely, tailpipe emissions (Zn, Pb, and V in fine mode), wear debris (Cu, Cd, Fe, Ga, Mn, Mo, Sb, and Sn), and resuspended dust (Ca, Mg, K, and Rb) - of airborne PM metals were categorized on the basis of the results of enrichment factor, correlation matrix, and principal component analysis. Size distributions of wear-originated metals resembled the pattern of crustal elements, which were predominated by super-micron particulates (PM1-10). By contrast, tailpipe exhaust elements such as Zn, Pb, and V were distributed mainly in submicron particles. By employing Cu as a tracer of wear abrasion, several inter-metal ratios - including Fe / Cu (14), Ba / Cu (1.05), Sb / Cu (0.16), Sn / Cu (0.10), and Ga / Cu (0.03) - served as fingerprints for wear debris. However, the data set collected in this work is useful for further studies on traffic emission inventory and human health effects of traffic-related PM.
Contribution of the road traffic to air pollution in the Prague city (busy speedway and suburban crossroads)
(2011-09-01)
Ondracek, J.
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Schwarz, J.
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Zdimal, V.
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Andelova, L.
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Vodicka, R.
Two measurement campaigns near busy freeway and suburban crossroad (different traffic intensity) were carried out in Prague city. Both of the two traffic related campaigns were supported with simultaneous measurements at suburban background site to compare measured values with corresponding city background. Extensive set of aerosol instrumentation was used during both campaigns at both measurement sites. Two aerosol spectrometer sets (SMPS and APS) were used to monitor aerosol particle number size distribution. Two BLPI provided information about mass size distribution and chemical composition of collected size resolved aerosol samples. The crossroad campaign was also supported by two EC/OC field analysers providing information about elemental and organic carbon concentrations. Consequent chemical analysis of collected size resolved samples comprised of ion chromatography (water soluble ions), PIXE (elements) and RBS (carbon). Results obtained from spectrometers and BLPIs showed that the main contribution of traffic in ultrafine size range can be attributed to direct exhaust emissions, while the coarse fraction was dominated mainly by regional background aerosol with small traces of brake and tyre abrasion as well as the resuspension of the road dust. Chemical analysis demonstrated that most of the water soluble ions can be found in fine fraction of mass distribution and mostly comes from regional background and long range transport. Most of major elements were found in coarse fraction of mass size distribution and it can be attributed to three different sources: abrasion of different vehicle parts (Fe, Cu, Mn and Zn), resuspension of the road dust (Si, Al, Ca) and long range transport or regional background (Ca and K). Elemental carbon concentration (diesel engine emissions) was found to be proportional to traffic intensity. (C) 2011 Elsevier Ltd. All rights reserved.
Effect of free electrons on nanoparticle charging in a negative direct current corona charger
(2008-10-13)
Aliat, A.
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Tsai, C. -J.
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Hung, C. -T.
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Wu, J. -S.
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機械工程學系
A two-dimensional numerical model is proposed in this letter to take into account the effects of free electrons on nanoparticle charging in a negative direct current wire-tube corona charger. Numerical results are in excellent agreement with the experimental data by using a capturing probability of electrons onto nanoparticles with a value of 0.013. These free electrons contribute greatly to the charging efficiency at high products of mean ion concentration and mean residence time, which explains very well the large discrepancy found in earlier models that considered only negative ions. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2967470]