| 英文摘要 |
In this project, chemical components and number concentration of PM2.5 were measured by Aerosol Chemical Speciation Monitor (ACSM) and SMPS in Northern Taiwan (Judong, Sinjhung and NCTU campus). The CMB results showed that SOA was the main component of organic aerosols in Judong and NCTU campus due to photochemical reaction, which accounted for 62.2 ± 16.3 and 65 ± 19.3% of total organic aerosols, respectively. In contrast, POA was the main component of organic aerosols in Sinjhung due to traffic emission, which accounted for 61 ± 2.54% of total organic aerosols. The PPPMF results underestimated the total organic aerosols at the three sites mentioned above by 19%, 14% and 13%, while the results analyzed by CMB showed almost no difference between measured values, suggesting that CMB is more accurate comparing to PPPMF. The conversion factors of OC to OM in Judong、Sinjhung and NCTU campus were 1.63 ± 0.76, 1.93 ± 1.84 and 1.61 ± 0.79, respectively. The average number concentration measured were (1.0 ± 0.6)×104 #/cm3 in Judong, having high correlation with O3 (R2 = 0.71), (1.1 ± 0.6) ×104 #/cm3 in Sinjhung, having high correlation with NOx and CO (both R2 = 0.78), and (1.09 ± 0.59) ×104 #/cm3 in NCTU campus , having high correlation with NOx and CO (both R2 = 0.84). The results measured by NanoScan SMPS matched well with those measured by SMPS for particle diameter (dm) smaller than 400nm with R2 of 0.99. Base on the number concentrations and chemical components measured above, the effective density in Judong、Sinjhung and NCTU campus sites were 2.45, 1.49 and 2.17 g/cm3, respectively.
In this study, the applicability of the ACSM for the real time atmospheric chemical composition measurement was investigated. In the beginning at Judong air monitoring station, agreement between soluble inorganic ions of aerosol chemical speciation monitor (ACSM), which used PM1 aerodynamic lens, and Particle into Liquid Sampler (PILS) was poor. There are two possible reasons. One reason is that only PM1 aerodynamic lens was available at Judong station which only detected particles less than 1 μm resulting in understimation of PM2.5 mass concentrations. The other reason is due to very low nitrate concentration, which was typically less than 1 μg m-3 at Judong station, while monodipsere nitrate particles of 300 nm was used to calibrate the ACSM. To overcome these shortcomings, a new PM2.5 lens was acquired to replace the PM2.5 lens of the ACSM at both Sinjhung station and National Chiao Tung University (NCTU) campus for conducting the comparsion test. Results showed that coefficients of determination (R2) were much better and that the NH4+and SO42- in PM2.5 measured by the ACSM were in good agreement with those measured by the PILS with R2 > 0.78.
In Sinjhung station, the study period was in summer. PM2.5 average concentration was 13.05±10.51 μg m-3, secondary inorganic aerosol (SIA) accounted for 45.36± 29.74%, secondary organic aerosol (SOA) accounted for 16.79± 13.48%, while primary organic aerosol (POA) accounted for 27.26 ± 38.79% in Sinjhung station. At NCTU campus, study period was in fall. PM2.5 average concentration was 29.04±17.72 μg m-3, SIA accounted for 51.80±27.66%, SOA accounted for 10.62±4.36%, while POA accounted for 6.26±5.28% at NCTU campus.
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