Browsing by Author "Wu, Yueh-Chuen"

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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.
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.
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.