| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 102 === In this study, the multi-filter PM10-PM2.5 sampler (MFPPS) 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 (FDMS-TEOM, Thermo, Model 1405-DF) were conducted at Taiwan Nation Chiao-Tung University (NCTU) campus. In order to evaluate the evaporation loss of fine particles (PM2.5), porous metal denuders (PMDs) were installed in sampling channels of the MFPPS to measure the concentration of evaporated ion species during sampling.
Results showed that the evaporation loss in PM2.5 was severe during sampling, accounting for 5.8 to 36.0 % of the corrected daily average PM2.5 concentration (PM2.5,Mcorr) 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 PM2.5,Mcorr, respectively, or 46.4 ± 19.2, 66.9 ± 18.5, and 74.4 ± 14.0 %, in the concentration of each species, respectively. The PM2.5,Mcorr concentration was decreased by 3.5 ± 1.8 % after 24-h conditioning, and was further decreased by 5.1 ± 1.7, 6.2 ± 2.5, 7.4 ± 3.3 and 8.5 ± 3.2 % after 48, 72, 96, and 120-h conditioning, respectively. Due to the evaporation loss, daily average PM2.5 concentrations measured by the WINS, Dichot, and MFPPS were lower than those the FDMS-TEOM by 16.6 ± 9.0, 15.2 ± 10.6 and 12.5 ± 8.8 %, respectively. When the MFPPS PM2.5 concentrations were corrected for the evaporated loss determined by the PMD, good agreement with those by the FDMS-TEOM was achieved. This indicates the FDMS-TEOM with the capability to adjust for sampling artifacts is an accurate real-time PM2.5 monitor.
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