| 摘要: | 中南半島生質燃燒產生大量的氣膠與氣體污染物，經長程傳輸廣泛影響到下風處的空氣品質。台灣正好位於生質燃燒煙霧氣團傳輸的下風處，是觀測中南半島生質燃燒傳輸污染物的最佳地點。為了避免受到地面污染物的干擾，本文從2007年7月到2008年4月在海拔2,862公尺的鹿林站進行大氣氣膠觀測，以瞭解非生質燃燒期間及受到生質燃燒氣團傳輸影響的氣膠特性。鹿林站生質燃燒期間的PM2.5細氣膠濃度為非生質燃燒期間的3倍，PM2.5銨根離子、硫酸根離子和硝酸根離子平均濃度則分別為1.50 µg m-3、4.06 µg m-3和0.50 µg m-3。生質燃燒污染物指標之一的鉀離子平均濃度為非生質燃燒期間的4倍。有機碳(OC)各成分濃度在生質燃燒期間都明顯增加，但元素碳(EC)只有EC1-OP增加。受到生質燃燒影響，氣膠水可溶有機碳的平均濃度為非生質燃燒期間的3.2倍，左旋葡萄糖的平均濃度為非生質燃燒時期的3倍，低分子量二元酸以oxalic acid為優勢物種，平均濃度為非生質燃燒期間的4.5倍。採樣期間氣流來源以逆溯軌跡線分類，並彙整各氣流軌跡分類的氣膠成分和非生質燃燒的氣膠成分比較，發現海洋傳輸所有氣膠成分濃度都是最低的；大陸傳輸氣流PM10-2.5粗粒徑氣膠濃度較高，且鈣離子濃度明顯高於其餘傳輸類型，推測是受到大陸沙塵傳輸影響；傳輸氣流經生質燃燒源區和中國南方PM2.5、鉀離子、oxalic acid以及左旋葡萄糖濃度都明顯較非生質燃燒期間為高。本文以電子顯微鏡觀察生質燃燒氣膠單顆粒影像，發現矩形結晶形態約佔觀測的氣膠數量70~80%，其次為焦球形態，葡萄串形態數量最少且顆粒最小。在鹿林站使用不同粒徑採樣器採集對流雲霧湧升時氣膠發現，PM1與PM2.5粒徑的氣膠成分濃度與平時差異不大，使用PM1與TSP氣膠的成分濃度差異較明顯。雲霧湧升時氣膠成分中以硝酸根離子去除的比例最高為0.41，其次是銨根離子與硫酸根離子。OC和EC的去除效率分別為0.20和0.22。受到雲霧影響時，PM2.5中的銨根離子、硫酸根離子與硝酸根離子濃度會明顯增加，顯示人為污染物隨著雲霧到來。 The tremendous amounts of aerosols and gas pollutants produced in Indo China will affect the downwind region as they are transported in a long distance. Taiwan is one of the best places to observe these transported pollutants as it is located in the downwind region. To circumbent the interference from ground level pollution, this study observed atmospheric aerosols at Mt. Lulin (2,862 m above sea level) from July 2007 to April 2008. The goal is to resolve the differences of aerosol property between biomass burning (BB) and non-biomass burning (NBB) periods. The PM2.5 level is three-fold during BB period as compared to that of NBB period. The PM2.5 ammonium ion, sulfate, and nitrate levels are 1.50 µg m-3, 4.06 µg m-3, and 0.50 µg m-3, respectively. Notably, the PM2.5 potassium ion as one of the markers for BB was four-fold as high as that during NBB period. As for the levels of the resolved carbonaceous fractions, organic carbons (OC) were increased significantly, while only EC1-OP was increased for elemental carbon (EC). Moreover, the mean values of water-soluble OC, levoglucosan, and low molecular-weight diacids during BB period were 3.2, 3, and 4.5 times, respecticely, in contrast to those during NBB period. Trajectory analysis for the air masses during observation period shows that the levels of aerosol components were the lowest for oceanic origin. It also shows that PM10-2.5 and calcium ion from China continent were apparently higher than those from other transport paths probably due to the influence of Asian dust. For the air masses from BB source region via southern China, PM2.5, potassion ion, oxalic acid, and levoglucosan were all higher during BB period than that of NBB period. For the aerosol morphology during BB period, the analysis of scanning electron microscopy reveals that rectangular crystal type is around 70-80% in the number of the observed aerosol particles followed by tar ball type and grape chain aggregrate takes the least. Different size cut samplers were adopted at Mt. Lulin to collect aerosols when in the uprising convective cloud, little difference was found for PM1 and PM2.5 aerosol components; however, a difference was exist for PM1 and TSP. Among aerosol components, the scavenging ratio was highest at 0.41 for nitrate followed by ammonium ion and sulfate. The scavenging ratio for OC and EC were 0.20 and 0.22, respectively. During cloud affecting period, the levels of PM2.5 ammonium ion, sulfate, and nitrate were significantly increased, which indicates anthropogenic pollutants were entrained in the cloud. |
