Browsing by Author "Chang, KF"

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A theoretical evaluation on the HNO3 artifact of the annular denuder system due to evaporation and diffusional deposition of NH4NO3-containing aerosols
(2002-09-01)
Chang, KF
;
Lu, CS
;
Bai, HL
;
Fang, GC
;
環境工程研究所
(A) mathematical model was developed to evaluate HNO3 artifact of the annular denuder system due to evaporation and diffusional deposition of nitrate-containing aerosols. The model performance was validated by comparing its numerical solutions with laboratory and numerical data available in the literature for evaporation and diffusional deposition of monodisperse and polydisperse NH4NO3 aerosols. Measurement artifacts were evaluated by varying typical sampling ranges of ambient temperature, HNO3 gas concentration, aerosol number concentration, aerosol mass median diameter, and nitrate mass fraction of < 2.5 mum aerosols to see their respective effects. Potential application of the present model on estimating HNO3 artifacts was demonstrated using literature data sampled in USA, Taiwan, Netherlands, Korea and Japan. Significant measurement artifact could be found in Taiwan and Netherlands due either to low HNO3 gas concentration and high nitrate concentration in < 2.5 mum aerosols or to high ambient temperature. (C) 2002 Elsevier Science Ltd. All rights reserved.
Estimation of PAHs dry deposition and BaP toxic equivalency factors (TEFs) study at Urban, Industry Park and rural sampling sites in central Taiwan, Taichung
(2004-05-01)
Fang, GC
;
Chang, KF
;
Lu, CS
;
Bai, HL
;
環境工程研究所
The concentrations of polycyclic aromatic hydrocarbons (PAHs) in gas phase and particle bound were measured simultaneously at industrial (INDUSTRY), urban (URBAN), and rural areas (RURAL) in Taichung, Taiwan. And the PAH concentrations, size distributions, estimated PAHs dry deposition fluxes and health risk study of PAHs in the ambient air of central Taiwan were discussed in this study. Total PAH concentrations at INDUSTRY, URBAN, and RURAL sampling sites were found to be 1650 +/- 1240, 1220 +/- 520, and 831 +/- 427 ng/m(3), respectively. The results indicated that PAH concentrations were higher at INDUSTRY and URBAN sampling sites than the RURAL sampling sites because of the more industrial processes, traffic exhausts and human activities. The estimation dry deposition and size distribution of PAHs were also studied. The results indicated that the estimated dry deposition fluxes of total PAHs were 58.5, 48.8, and 38.6 mug/m(2)/day at INDUSTRY, URBAN, and RURAL, respectively. The BaP equivalency results indicated that the health risk of gas phase PAHs were higher than the particle phase at three sampling sites of central Taiwan. However, compared with the BaP equivalency results to other studies conducted in factory, this study indicated the health risk of PAHs was acceptable in the ambient air of central Taiwan. (C) 2004 Elsevier Ltd. All rights reserved.
Measurement of atmospheric particles and anionic species across central Taiwan
(2003)
Fang, GC
;
Chang, KF
;
Lu, CS
;
Bai, HL
;
環境工程研究所
The ambient air concentrations and fluxes of various anionic species were sampled by MOUDI, TSP and dry deposition plates at a traffic sampling site in Taichung, central Taiwan. In the sampling period, from September to December 2000, the ambient air particle concentrations (PM1, PM2.5, PM10 and TSP) were lower in the September than in the other three months (October to December). The reason is that the northwest wind brought more particles (diameter less than 10 mum) and the higher wind speed caused higher dry deposition fluxes and TSP concentrations in the last three months. The anion species percentages of TSP were 0.24%, 13.7%, 0.52%, 12.0%, 18.9% and 54.6% for F-, Cl-1 Br-1 NO2-1 NO3 and SO42-, respectively. The results revealed that SO42-, NO3, Cl- and NO2- were the dominant species at the traffic sampling site. The ion-size distributions of Cl-, NO2- and NO3 were unimodal, the main peak being between 3.2 and 5.6 mum. In contrast, the size distribution Of SO42- was bimodal, with the main peaks in the particle size ranges 0.32-0.56 mum and 3.2-5.6 mum. The ambient average particle dry deposition flux was 6.28 mug/m(2)/s, and the dry deposition fluxes were 0.01, 94.6, 0.05, 34.7, 72.2 and 376.4 ng/m(2)/s for F-, Cl-, Br, NO2-, NO3- and SO42-, respectively. The dry deposition velocities were 3.10, 0.03, 3.67, 0.05, 1.54, 2.03 and 3.67 cm/s for F-, Cl-, Br-, NO2-, NO3- and SO42-, respectively.
Particle size distribution and anion content at a traffic site in Sha-Lu, Taiwan
(2001-11-01)
Chang, KF
;
Fang, GC
;
Lu, CS
;
Bai, HL
;
環境工程研究所
Ambient air particle concentrations were sampled by two total suspended particle (TSP) samplers, PM10/PM2.5 specific sampler and micro-orifice uniform deposit impactor (MOUDI) during July-October 2000 at a traffic sampling site in central Taiwan. The average TSP concentration (194 mug/m(3)) was about a factor of two higher than that of the fraction <2.5 mum (93.2 mug/m(3)). The mean level of the fraction < 10 mum collected by MOUDI (93.2 mug/m(3)) was about 11/2 times higher than that of the size class <2.5 mum (43.8 mug/m(3)). Furthermore, this fraction showed a certain correlation with the TSP concentration. The particle size distribution was bimodal in the ambient air at the traffic site. The major peaks appear at particle diameters between 0.56-1.0 and 3.2-5.6 mum. The percentages of anions contained in TSP were 0.23% F-, 13.7% Cl-, 0.52% Br-, 12.0% NO3-, 18.9% NO2-, and 54.6% SO42-. The Cl-, NO2-, and NO3- size distributions were all unimodal and the major peaks appeared at 3.2-5.6 mum. The SO42- size distribution was bimodal, with major peaks at 0.32-0.56 and 3.2-5.6. (C) 2001 Elsevier Science Ltd. All rights reserved.
Sources of sampling error for field measurement of nitric acid gas by a denuder system
(2003-03-01)
Bai, H
;
Lu, C
;
Chang, KF
;
Fang, GC
;
環境工程研究所
Field measurements of atmospheric HNO3 gas by a denuder system equipped with four annular denuders were conducted in Taiwan. The positive errors from interfering N-compounds as well as the negative errors from incompleteness of the apparent absorption of the HNO3 gas. as sampled by one NaCl-denuder, were quantitatively determined and the error sources were identified. It is found that the concentrations of positive error and negative error might cancel each other resulting in less difference between the measured and the true HNO3 concentrations. The atmospheric HNO3 concentration and the ambient temperature were the major factors that influence the degree of negative errors. The apparent absorption efficiency might decrease to less than 80% if the HNO3 gas concentration were lower than 0.3 mug m(-3) or the ambient temperature were over 28degreesC. There are also evidences showed that the positive errors were from both interfering N-containing gases and nitrate-containing particles. (C) 2003 Elsevier Science Ltd. All rights reserved.
Toxic equivalency factors study of polycyclic aromatic hydrocarbons (PAHs) in Taichung City, Taiwan
(2002)
Fang, GC
;
Chang, KF
;
Lu, CS
;
Bai, HL
;
環境工程研究所
Airborne particles and polycyclic aromatic hydrocarbons (PAHs) in industrial, background and urban atmosphere environments were investigated using toxic equivalent factors (TEFs) in central Taiwan during the period of August-/December 2002. Concentrations of airborne particles were 93.4, 81.3 and 102.4 mug/m(3) for industrial, background and urban sites, respectively. Concentrations of 21 gaseous PAHs were 1530, 759 and 1030 ng/m(3) for industrial, background and urban sites, respectively; for carcinogenic activity of gaseous PAHs, the benzo[ a] pyrene (BaP) equivalent concentrations were 17.0, 7.29 and 12.6 ng/m(3) for industrial, background and urban sites, respectively. Twenty-one particle-bound PAHs were only 10% of the 21 gaseous PAHs. Dibenzo(a, h) anthracene (DBA) serves as a surrogate to explain the carcinogenic activity of PAH mixtures in central Taiwan because its carcinogenicity is a high percentage of the total carcinogenic activity. During the sampling period, temperature inversion from a cold front from China occurred, leading to average daily temperatures of 16degreesC. These cold fronts caused atmospheric particles and pollutants to accumulate in the troposphere, leading to extremely high concentrations of airborne particles and both gaseous and particle-bound PAHs in central Taiwan.