Browsing by Author "Liu, Chun-Nan"

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A Novel Multifilter PM(10)-PM(2.5) Sampler (MFPPS)
(2011-01-01)
Liu, Chun-Nan
;
Chen, Sheng-Chieh
;
Tsai, Chuen-Jinn
;
環境工程研究所
;
Institute of Environmental Engineering
A novel multifilter PM(10)-PM(2.5) sampler (MFPPS) that enables the collection of four PM(10) and four PM(2.5) samples simultaneously has been developed and tested. The MFPPS uses a PM(10) impactor as the inlet and operates at 33.4 L/min. After the inlet, the aerosol flow is divided half by a Y-type fitting. Half of the flow is directed into four PM(10) filter cassettes, while the other half is directed into four PM(2.5) filter cassettes after the aerosols are further classified by a PM(2.5) impactor. An active flow control system consisting of two mass flow controllers (MFCs), one for PM(10) and the other for PM(2.5), is used to fix the total flow rate of 16.7 L/min for four PM(10) or four PM(2.5) channels based on the ambient pressure and temperature. To ensure flow rate uniformity through each of the four PM(10) or four PM(2.5) filter cassettes, an orifice is assembled behind each of the filter cassettes to increase the pressure drop, such that the flow rates of eight sampling lines are nearly equal using just two MFCs. The MFPPS was calibrated in the laboratory for particle collection efficiency curves first. Then, the ambient PM concentrations were compared with those of other two collocated FRM samplers, the dichotomous PM(10) and the EPA WINS PM(2.5) sampler in the field study. Calibration results showed the cutoff aerodynamic diameters of the PM(10) and PM(2.5) impactors were 9.8 +/- 0.1 and 2.5 +/- 0.05 mu m, respectively. Field comparison results indicated PM(10) and PM(2.5) concentrations agreed well with the other two PM samplers.
A Novel Multifilter PM10-PM2.5 Sampler (MFPPS)
(2011-01-01)
Liu, Chun-Nan
;
Chen, Sheng-Chieh
;
Tsai, Chuen-Jinn
;
環境工程研究所
;
Institute of Environmental Engineering
A novel multifilter PM10-PM2.5 sampler (MFPPS) that enables the collection of four PM10 and four PM2.5 samples simultaneously has been developed and tested. The MFPPS uses a PM10 impactor as the inlet and operates at 33.4 L/min. After the inlet, the aerosol flow is divided half by a Y-type fitting. Half of the flow is directed into four PM10 filter cassettes, while the other half is directed into four PM2.5 filter cassettes after the aerosols are further classified by a PM2.5 impactor. An active flow control system consisting of two mass flow controllers (MFCs), one for PM10 and the other for PM2.5, is used to fix the total flow rate of 16.7 L/min for four PM10 or four PM2.5 channels based on the ambient pressure and temperature. To ensure flow rate uniformity through each of the four PM10 or four PM2.5 filter cassettes, an orifice is assembled behind each of the filter cassettes to increase the pressure drop, such that the flow rates of eight sampling lines are nearly equal using just two MFCs. The MFPPS was calibrated in the laboratory for particle collection efficiency curves first. Then, the ambient PM concentrations were compared with those of other two collocated FRM samplers, the dichotomous PM10 and the EPA WINS PM2.5 sampler in the field study. Calibration results showed the cutoff aerodynamic diameters of the PM10 and PM2.5 impactors were 9.8 +/- 0.1 and 2.5 +/- 0.05 mu m, respectively. Field comparison results indicated PM10 and PM2.5 concentrations agreed well with the other two PM samplers.
Characteristic of nanoparticles generated from different nano-powders by using different dispersion methods
(2012-04-01)
Tsai, Chuen-Jinn
;
Lin, Guan-Yu
;
Liu, Chun-Nan
;
He, Chi-En
;
Chen, Chun-Wan
A standard rotating drum with a modified sampling train (RD), a vortex shaker (VS), and a SSPD (small-scale powder disperser) were used to investigate the emission characteristics of nano-powders, including nano-titanium dioxide (nano-TiO2, primary diameter: 21 nm), nano-zinc oxide (nano-ZnO, primary diameter: 30-50 nm), and nano-silicon dioxide (nano-SiO2, primary diameter: 10-30 nm). A TSI SMPS (scanning mobility particle sizer), a TSI APS (aerodynamic particle sizer), and a MSP MOUDI (micro-orifice uniform deposit impactor) were used to measure the number and mass distributions of generated particles. Significant differences in specific number and mass concentration or distributions were found among different methods and nano-powders with the most specific number and mass concentration and the smallest particles being generated by the most energetic SSPD, followed by VS and RD. Near uni-modal number or mass distributions were observed for the SSPD while bi-modal number or mass distributions existed for nano-powders except nano-SiO2 which also exhibited bimodal mass distributions. The 30-min average results showed that the mass median aerodynamic diameter (MMAD) and number median diameter (NMD) of the SSPD ranged 1.1-2.1 mu m and 166-261 nm, respectively, for all three nano-powders, which were smaller than those of the VS (MMAD: 3.3-6.0 mu m and NMD: 156-462 nm), and the RD (MMAD: 5.2-11.2 mu m and NMD: 198-479 nm). For nano-particles (electric mobility diameter < 100 nm), specific mass concentrations were nearly negligible for all three nano-powders and test methods. Specific number concentrations of nano-particles were low for the RD tester but were elevated when more energetic VS and SSPD testers were used. The quantitative size and concentration data obtained in this study is useful to elucidate the field emission and personal exposure data in the future provided that particle loss in the generation system is carefully assessed.
Collection efficiency and interstage loss of nanoparticles in micro-orifice-based cascade impactors
(2013-04-01)
Liu, Chun-Nan
;
Awasthi, Amit
;
Hung, Yi-Hung
;
Tsai, Chuen-Jinn
;
環境工程研究所
In this study, two micro-orifice-based cascade impactors, including the micro-orifice uniform deposit impactor (MOUDI, MSP Model 110) and the NCTU micro-orifice cascade impactor (NMCI), were tested for the collection efficiency and interstage loss of nanoparticles. In the NMCI, new nozzle plates with smooth nozzle shape made by the LIGA (Lithography, Electroplating, and Molding) process were used to replace the 7th-10th stages in one of the MOUDI. Test results show that after adjusting proper S/W ratios (S: jet to plate distance, W: nozzle diameter) to 2.52, 3.01, 13.44, and 24.75 for the 7th, 8th, 9th and 10th stage of the NMCI, respectively, and 5.56, 11.18, 9.3, and 10.9 for the 7th, 8th, 9th and 10th stage of the MOUDI, respectively, the cutoff aerodynamic diameters (d(pa50)) are close to the nominal values given in Marple et al. (1991). Different S/W ratios are needed due to differences in the nozzle shape and nozzle diameter between two cascade impactors. Total interstage loss of nanoparticles from the inlet to the 6th-10th stage of the MOUDI exists due to the convection-diffusion mechanism, which increases with decreasing d(pa). For the MOUDI, total loss is 2.9-15.3 % (d(pa): 105.8 to 15.4 nm) for the inlet to the 6th stage and it increases to 20.1-26.1 % (d(pa): 23 to 15.4 nm) for the inlet to the 10th stage, respectively. Similar but slightly lower loss also exists in the NMCI. Field comparison tests in the ambient air show that mass size distributions measured by the MOUDI agree well with those of the NMCI. Finally, nozzle clogging tests using high concentration incense smokes indicate that the NMCI has a much less tendency for particles to clog in the nozzles than the MODUI. (C) 2012 Elsevier Ltd. All rights reserved.
Design and Testing of the NCTU Micro-Orifice Cascade Impactor (NMCI) for the Measurement of Nanoparticle Size Distributions
(2015-01-01)
Chien, Chih-Liang
;
Tien, Chi-Yu
;
Liu, Chun-Nan
;
Ye, Huajun
;
Huang, Wei
The NCTU micro-orifice cascade impactor (NMCI) was redesigned and tested to enable the measurement and adjustment of the jet-to-plate distance (S) of the impactors by using a micrometer. Each stage of the NMCI contains an impaction plate and a nozzle plate which are separated. The bottom casing for impaction plate assembly and the nozzle plate holder of each stage are separated. Calibration results show that the cutoff aerodynamic diameter (d(pa50)) of the three lower stages (d(pa50) = 180, 100, and 56 nm) are close to the nominal values given in Marple et al. (1991). In addition, the S/W (W: nozzle diameter) effects on the d(pa50) for the three lower stages were investigated and an empirical equation was developed to facilitate the prediction of d(pa50) when the nozzle diameters may change slightly from one batch to another. The relationship between the nozzle diameter and pressure drop of the micro-orifice impactors at the fixed operational flow rate of 30 L/min was also established so that the nozzle diameters can be predicted from the pressure drop measurement. An empirical equation was proposed to express the correlation between the dimensionless cutoff size and the S/W ratio when considering isentropic flow to facilitate the design of microorifice impactors for S/W > 4. It is expected that the present NMCI could improve the accuracy of size classification of submicron particles below 180 nm, especially for nanoparticles.
Differences in 24-h average PM2.5 concentrations between the beta attenuation monitor (BAM) and the dichotomous sampler (Dichot)
(2013-08-01)
Liu, Chun-Nan
;
Awasthi, Amit
;
Hung, Yi-Hung
;
Gugamsetty, Balakrishnaiah
;
Tsai, Chuen-Jinn
In this study, PM2.5 concentrations were measured simultaneously by a Dichotomous sampler (Dichot, Model SA241, Andersen Inc., Georgia, USA) (PM2.5,D) and a beta attenuation monitor (BAM) (PM2.5,B) at each of three air monitoring stations in Taiwan. Results show that PM2.5,B concentrations measured by the VEREWA-F701 BAM (without federal equivalent method (FEM) designation) are consistently higher than PM2.5,D concentrations by 58.4 37.4% at Jhongshan station, while less overestimation exists at Sinjhuang and judong stations, which is 29.8 +/- 20.2 and 28.4 +/- 19.0%, respectively, where the earlier version of the Met-One BAM-1020s (without FEM designation) are used. Different factors influencing the overestimation, which include aerosol water content, volatilization of inorganic species and positive artifacts due to acid gas adsorption by the glass fiber filter tapes were studied for the BAM-1020. Results show that the overestimation is mainly caused by the positive artifacts due to acid gas adsorption by the glass fiber filter tapes used in the BAM-1020. Aerosol water content and volatilization loss of inorganic semi-volatile species are found to be less important to the overestimation. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
Drag Coefficient of a Spherical Particle Attached on the Flat Surface
(2011-10-01)
Liu, Chun-Nan
;
Chien, Chih-Liang
;
Lo, Chu-Chun
;
Lin, Guan-Yu
;
Chen, Sheng-Chieh
The previous analytical solution for the drag coefficient (C(d)) for a spherical particle attached on the flat surface, which was derived by O'Neill (1968), is only valid in the creeping flow conditions. It is important to extend O'Neill's formula to cover a wide range of particle Reynolds number (Re(p)). In this study, the drag coefficient was calculated numerically to cover Re(p) from 0.1 to 250. For a particle suspended in the air, an empirical drag coefficient exists, which is defined as C(d) = f x 24/Re(p), where f is a correction factor depending on Re(p). The applicability of the correction factor f for O'Neill's analytical equation for the spherical particle attached on the flat surface for Re(p) = 0.1 to 250 was examined in this study.
Novel Active Personal Nanoparticle Sampler for the Exposure Assessment of Nanoparticles in Workplaces
(2012-04-17)
Tsai, Chuen-Jinn
;
Liu, Chun-Nan
;
Hung, Shao-Ming
;
Chen, Sheng-Chieh
;
Uang, Shi-Nian
A novel active personal nanoparticle sampler (PENS), which enables the collection of both respirable particulate mass (RPM) and nanoparticles (NPs) simultaneously, was developed to meet the critical demand for personal sampling of engineered nanomaterials (ENMs) in workplaces. The PENS consists of a respirable cyclone and a micro-orifice impactor with the cutoff aerodynamic diameter (d(pa50)) of 4 mu m and 100 nm, respectively. The micro-orifice impactor has a fixed micro-orifice plate (137 nozzles of 55 mu m in the inner diameter) and a rotating, silicone oil-coated Teflon filter substrate at 1 rpm to achieve a uniform particle deposition and avoid solid particle bounce. A final filter is used after the impactor to collect the NPs. Calibration results show that the d(pa50) of the respirable cyclone and the micro-orifice impactor are 3.92 +/- 0.22 mu m and 101.4 +/- 0.1 nm, respectively. The d(pa50) at the loaded micro-Al2O3 mass of 0.36-3.18 mg is shifted to 102.9-101.2 nm, respectively, while it is shifted to 98.9-97.8 nm at the loaded nano-TiO2 mass of 0.92-1.78 mg, respectively. That is, the shift of d(pa50) due to solid particle loading is small if the PENS is not overloaded. Both NPs and RPM concentrations were found to agree well with those of the IOSH respirable cyclone and MOUDI. By using the present PENS, the collected samples can be further analyzed for chemical species concentrations besides gravimetric analysis to determine the actual exposure concentrations of ENMs in both RPM and NPs fractions in workplaces, which are often influenced by the background or incident pollution sources.
Sampling and conditioning artifacts of PM2.5 in filter-based samplers
(2014-03-01)
Liu, Chun-Nan
;
Lin, Sih-Fan
;
Awasthi, Amit
;
Tsai, Chuen-Jinn
;
Wu, Yueh-Chuen
Field studies were conducted at Taiwan National Chiao-Tung University (NCTU) campus to evaluate the evaporation loss of fine particles (PM2.5) collected by the multi-filter PM10-PM2.5 sampler (MFPPS), which was collocated with a dichotomous sampler (Dichot, Andersen, Model SA-241), a WINS PM2.5 sampler (Thermo, Model 2000-FRM), and a tapered element oscillating microbalance with the filter dynamic measurement system (TEOM-FDMS, Thermo, Model 1405-DF). Porous-metal denuder samplers (PDSs) were installed in sampling channels of the MFPPS to measure the concentration of evaporated ion species. Results showed that the evaporation loss in PM2.5 was severe during sampling, accounting for 5.8-36.0% of the corrected PM2.5 concentration and the percentage increased with decreasing loaded particle mass and increasing filtration velocity. During 24-h sampling, the evaporated NH4+, NO3- and Cl- concentrations accounted for 9.5 +/- 6.2, 5.4 +/- 3.7, and 2.0 +/- 1.3% in corrected PM(2.)5 concentration, respectively, or 46.4 +/- 19.2, 66.9 +/- 18.5, and 74.4 +/- 14.0% in the concentration of each species, respectively. Due to the evaporation loss, PM2.5 concentrations measured by the WINS, Dichot, and MFPPS were lower than those the TEOM-FDMS by 16.6 +/- 9.0, 15.2 +/- 10.6 and 12.5 +/- 8.8%, respectively. When the MFPPS PM(2.)5 concentrations were corrected for the evaporated loss determined by the PDS, good agreement with those by the TEOM-FDMS was achieved. (C) 2013 Elsevier Ltd. All rights reserved.
Source Characterization and Apportionment of PM10, PM2.5 and PM0.1 by Using Positive Matrix Factorization
(2012-08-01)
Gugamsetty, Balakrishnaiah
;
Wei, Han
;
Liu, Chun-Nan
;
Awasthi, Amit
;
Hsu, Shih-Chieh
Ambient Particulate Matters (PM10, PM2.5 and PM0.1) were investigated at Shinjung station in New Taipei City, Taiwan. Samples were collected simultaneously using a dichotomous sampler (Andersen Model SA-241) and a MOUDI (MSP Model 110) over a 24-h period from May 2011 to November 2011 at Shinjung station. Samples were analyzed for metallic trace elements using ion coupled plasma mass spectroscopy (ICP-MS) and ionic compounds by ion chromatography (IC). The average concentrations of PM10, PM2.5 and PM0.1 were found to be 39.45 +/- 11.58, 21.82 +/- 7.50 and 1.42 +/- 0.56 mu g/m(3), respectively. Based on the chemical information, positive matrix factorization (PMF) was used to identify PM sources. A total of five source types were identified, including soil dust, vehicle emissions, sea salt, industrial emissions and secondary aerosols, and their contributions were estimated using PMF. The crustal enrichment factors (EF) were calculated using Al as a reference for the trace metal species to identify the sources. Conditional probability functions (CPF) were computed using wind profiles and factor contributions. The results of CPF analysis were used to identify local point sources. The results suggest a competitive relationship between anthropogenic and natural source processes over the monitoring station.
"Source Characterization and Apportionment of PM10, PM2.5 and PM0.1 by Using Positive Matrix Factorization"
(2012-08-01)
Gugamsetty, Balakrishnaiah
;
Wei, Han
;
Liu, Chun-Nan
;
Awasthi, Amit
;
Hsu, Shih-Chieh
"Ambient Particulate Matters (PM10, PM2.5 and PM0.1) were investigated at Shinjung station in New Taipei City, Taiwan. Samples were collected simultaneously using a dichotomous sampler (Andersen Model SA-241) and a MOUDI (MSP Model 110) over a 24-h period from May 2011 to November 2011 at Shinjung station. Samples were analyzed for metallic trace elements using ion coupled plasma mass spectroscopy (ICP-MS) and ionic compounds by ion chromatography (IC). The average concentrations of PM10, PM2.5 and PM0.1 were found to be 39.45 +/- 11.58, 21.82 +/- 7.50 and 1.42 +/- 0.56 mu g/m(3), respectively. Based on the chemical information, positive matrix factorization (PMF) was used to identify PM sources. A total of five source types were identified, including soil dust, vehicle emissions, sea salt, industrial emissions and secondary aerosols, and their contributions were estimated using PMF. The crustal enrichment factors (EF) were calculated using Al as a reference for the trace metal species to identify the sources. Conditional probability functions (CPF) were computed using wind profiles and factor contributions. The results of CPF analysis were used to identify local point sources. The results suggest a competitive relationship between anthropogenic and natural source processes over the monitoring station."
Theoretical model for the evaporation loss of PM2.5 during filter sampling
(2015-05-01)
Liu, Chun-Nan
;
Lin, Sih-Fan
;
Tsai, Chuen-Jinn
;
Wu, Yueh-Chuen
;
Chen, Chung-Fang
The evaporation losses of PM2.5 particles in eight different size ranges corresponding to the 4th-10th stages and after filter of the MOUDI were calculated theoretically and then integrated to obtain the total PM2.5 evaporation loss. Results show that when PM2.5 particles are nearly neutral with pH in the range of 7-8, the evaporated concentrations predicted by the present model agree well with the experimental data with an average absolute difference of 20.2 +/- 11.1%. When PM2.5 aerosols are acidic with pH less than 3.5, additional loss of nitrate and chloride can occur due to chemical interactions between collected particles and strong acids which are not considered in the present model. Under pH neutral conditions, the theoretical model was then used to examine the effect of PM2.5 concentration, gas-to-particle ratio, ambient temperature and relative humidity on the extent of evaporation loss. Results show that evaporated PM2.5 concentration increases with increasing temperature and decreasing relative humidity, PM2.5 concentration and gas-to-particle ratio. (C) 2015 Elsevier Ltd. All rights reserved.