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|關鍵字:||size distributions;粒徑分佈;MOUDI;trimodal size distributions;VARIMAX-rotated principal component analyses;SOR;NOR;微孔均勻沈積衝擊器;三峰分佈;主成分因子分析;硫氧化比值;氮氧化比值||出版社:||環境工程學系||摘要:||
分析結果顯示採樣期間阿里山之大氣懸浮微粒PM2.5平均質量濃度為21.5 ±10.5ug/m3，PM2.5-10平均質量濃度為8.0±4.2ug/m3，台中都會區PM2.5及PM2.5-10平均質量濃度為55.7±9.1ug/m3及26.6±6.9ug/m3，台中海岸平原區大氣懸浮微粒PM2.5及PM2.5-10平均質量濃度為34.0±7.9ug/m3及27.5±6.3ug/m3。阿里山地區之PM10平均質量濃度約為台中都會區及海岸平原區的36及48 ％。研究也顯示阿里山的細粒質量濃度約佔PM10質量濃度的73 ％。阿里山地區大氣中之硫酸鹽、硝酸鹽以及銨鹽濃度明顯低於都會及海岸平原區，尤其以硝酸鹽差異性最大，都會區的硝酸鹽是海岸平原區的1.5 ~ 2倍，但在阿里山地區PM10氣膠中硝酸鹽佔不到5 ％。
於粒徑分佈方面，阿里山之硫酸鹽、硝酸鹽及銨鹽粒徑皆呈現三峰分佈，硫酸鹽波峰粒徑分布在0.85 ~ 1.7um之粒徑範圍，與平地之硫酸鹽主要粒徑分佈範圍0.56 ~ 1.0um相比稍大，推測與阿里山高相對濕度有關。
The purpose of this study was to understand the chemical compositions and the size distributions of atmospheric particulates sampled in Mt. Ali remote area. The ambient particulates were sampled with a micro-orifice uniform deposit impactor (MOUDI) and two dichotomous samplers during September-November, 1998 and March, 1999. The sampling site was located at Mt. Ali weather service office at an elevation of 2413 m above sea level. The collected samples were analyzed for water soluble ions, elemental carbon (EC), organic carbon (OC), and metallic constituents. This study also monitored SOX, NOX, O3, and PM10 during the sampling period. In the same time, the aerosol sampling was conducted in Taichung urban area and coastal suburban area for comparison.
The results showed that the mean mass concentrations were 21.5 10.5 g/m3 for fine particles and 8.0 4.2 g/m3 for coarse particles in the Mt. Ali, 55.7 9.1 g/m3 for fine particles and 26.6 6.9 g/m3 for coarse particles in the Taichung urban area, and 34.0 7.9 g/m3 for fine particles and 27.5 6.3 g/m3 for coarse particles in the Taichung coastal suburban area. The PM10 concentration in remote site was roughly 36 % of those in Taichung city, and 48 % of those in the suburban area on average. The mass of PM2.5 was approximately 73 % of the PM10. Mean concentrations of SO42-, NO3-, and NH4+ in the Mt. Ali remote area were significantly lower than those in the urban and suburban areas. Particularly the nitrate in the urban area was approximately 1.5-2 times more than those in the coastal area. On average, nitrate was found less than 5 % of the PM10 particles in the remote area.
The size distributions of SO42-, NO3-, and NH4+ showed that the particles in the Mt. Ali remote area had trimodal size distributions. The major peak was located at 0.56 - 1.0 m size range in the urban and the coastal areas. Howeven, the peak was located at 0.85-1.7 m size range in the Mt. Ali. The sizes might grew according to relative humidity.
The VARIMAX-rotated principal component analyses identified three major components accounting for approximately 60 % of total variance. The possible three sources were traffic vehicles, agriculture burning ,and secondary aerosols.
SOX concentration in the Mt. Ali were roughly one - fourth of those at the surface, NOX concentration were roughly one-seventh of those at the surface, and O3 concentration were the double of those at the surface. The values of Sulphur oxidation ratio ( SOR ) at Mt. Ali was 0.97, while the Nitrogen oxidation ratio ( NOR ) was 0.25 indicating the sulfate and nitrate aerosol most likely brought by long-range transportation.
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