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Variation in Formation and Source Apportionment of Dicarboxylic Acids in Nanoaerosol during Pm Episodes and Clear-Air Periods
nano-dicarboxylic acid aerosol,size distribution
Gaussian trajectory transfer-coefficient model (GTx)
|上傳時間: ||2010-03-26 16:35:38 (UTC+8)|
|摘要: ||二元酸是大氣環境中氣膠的重要組成之一，來自石化燃料燃燒及人為與生物源的有機前驅物的光化反應導致。二元酸的存在會改變氣膠在大氣中的尺寸及雲凝結的成核反應，進而影響降雨及氣候，已有證據指出因二元酸會折射來自太陽輻射而直接及間接影響地球的輻射平衡，從而抗衡因溫室氣體導致的全球暖化現象。然而目前對於微粒二元酸的形成及微粒粒徑分佈的相關研究，國內外尚少瞭解，尤其是高污染時期及農廢燃燒事件日發生時之5-100 nm 的奈米氣膠及粒徑至18 μm 的氣膠二元酸分佈特性的研究尚有很大探討空間，乃至於乾淨大氣的奈米二元酸特性亦尚未深入瞭解。本研究團隊自93 年8 月起已有二年以上研究基礎，期間除了開發大氣次微米微粒二元酸分析技術，探討PM10、PM2.5、大於0.057μm 以上粒徑分階的次微米氣膠二元酸特性及發展軌跡傳遞係數模式(GTx)之氣膠二元酸光化學機制模組外，發現台南郊區大氣氣膠組成來自點、線、面污染源的貢獻比例平均合計為64%，污染軌跡的邊界起始點及高空沉降的貢獻比例平均可達36%，顯示各項污染來源均具不可忽略的貢獻分配。然而這些研究多屬短期，且針對奈米粒徑的研究才剛展開，對於二元酸初始氣膠的物理化學特性的研究並不完整，且缺乏長期從背景環境、乾淨大氣時期、高污染及農廢燃燒時期的奈米二元酸氣膠特性及其污染貢獻分配。因此本研究將以三年時間探討不同大氣污染時期之奈米二元酸氣膠特性及其污染貢獻分配，藉此可探討奈米二元酸之初始粒徑生成變異，氣膠二元酸物種之關聯性及其不同大氣污染狀態的污染來源。本三年期計畫之第一年度計畫(96 年8 月－97 年7 月)，在代表南台灣地表背景大氣環境之墾丁國家公園，進行長期大氣背景奈米微粒及粒徑至18 μm 的氣膠二元酸之粒徑生成變異探討，並模擬高斯軌跡傳遞係數模式(GTx)加入本研究修正之背景氣膠二元酸及無機鹽類轉換機制模組之敏感度分析。第二年度計畫(97 年8 月－98 年7 月)，在台南郊區，長期進行乾淨大氣時期之奈米微粒及粒徑至18 μm 的氣膠二元酸之生成變異探討，並探討乾淨大氣時期之奈米微粒與光化條件的關聯性及氣膠污染來源解析。此外探討第一年計畫所獲致的背景二元酸氣膠特性與第二年計畫之乾淨大氣時期的郊區二元酸氣膠特性差異及原由。第三年度計畫(98 年8 月－99 年7 月)，在台南郊區，進行高污染及農廢燃燒時期的奈米二元酸氣膠之粒徑生成特性探討，並將計畫三年所持續累積的高污染及農廢燃燒事件日的奈米二元酸氣膠特性進行探討，瞭解在高污染及農廢燃燒事件日與背景及乾淨大氣時期的奈米二元酸氣膠粒徑分佈差異，並討論不同污染類型的二元酸氣膠粒徑分佈與光化環境的關聯性，最後探討高污染及農廢燃燒事件日之氣膠污染貢獻來源。|
Dicarboxylic acids, which originate from burning of petroleum fuel as well as from man-made and natural photochemical precursors, are one of the important atmospheric aerosols. Their existence in the atmosphere will change the size and chemical reactions of cloud condensation nuclei (CCN) to influence precipitation and climate. There are also evidences showing that dicarboxylic acids will refract solar radiation thus directly or indirectly affect the global radiation balance to counterbalance the global warming caused by greenhouse gases. However, the formation and size distribution of fine dicarboxylic acids in the atmospheric particles have not been fully studied and understood by either native or international researchers. Thus, there is still much room for studying the distribution characteristics of 5-100 nm up to 18 μm aerosols that occur in the atmosphere during the high-pollution period or the agricultural waste-burning period. Even the characteristics of dicarboxylic acids in the clean atmosphere have not been studied in-depth. This research group has accumulated more than 2-year experience on studying dicarboxylic acids since 2004. In addition to developing the technology for analyzing atmospheric submicron dicarboxylic acids, investigating the characteristics of PM10, PM2.5 and 0.057 μm and above aerosol particles, developing the Gaussian trajectory transfer-coefficient model (GTx) to simulate chemical reaction mechanisms for aerosol dicarboxylic acids, the research reveals that the average ratio is 64% for point, line and area sources contributing to atmospheric aerosol in Tainan suburban area and that the average ratio of contribution due to upwind and top boundary precipitation reaches 36%. Hence the pollutant may come from different sources and the contributions of all resources cannot be ignored. However, the results so-far accomplished are mostly based on short-time studies; the research to study nano-aerosol just started. The investigation on the physical and chemical characteristics of the aerosol formation of dicarboxylic acids is not completed because it lacks the collection of long-term background information during clear-air, high-pollution and agricultural-burning periods for nano-dicarboxylic acid aerosols on their characteristics and contributions to air pollution. Hence, this three-year research will investigate aerosol characteristics and contribution distribution to aerosol of nano-dicarboxylic acid during periods of various atmospheric pollutions. Formation variations of the dicarboxylic acid aerosols, correlations among carboxylic acid species and their various pollution sources will also be studied in this research. The first year (Aug. 2007－July 2008) will be devoted to studying the long-term background atmospheric nano aerosol particles up to 18 μm at Kenting National Park and their formation variations as well as including the use of GTx Model for simulating the conversion between the background aerosol dicarboxylic acids and inorganic salts and performing sensitivity analyses. The second-year research (Aug. 2008－July 2009) will study the long-term size variations of nano up to 18 μm dicarboxylic acid aerosols in the atmosphere during the clear-air period in addition to carrying out the analyses of the correlation between nano aerosol and photochemical conditions as well as source apportionments to aerosol. The background information on dicarboxylic acid aerosol characteristics as collected during the first year and the characteristic difference and sources of dicarboxylic acids in the suburban atmosphere during the clear-air period as collected during the second year will be combined to perform further in-depth analyses. The third-year study (Aug. 2009－July 2010) will include investigating the formation characteristics of nano dicarboxylic acids during high-pollution and agricultural waste-burning periods. Additionally, the information accumulated during the three-year study period will be analyzed to study the characteristics of nano dicarboxylic acids observed during high-pollution and agricultural waste-burning periods in order to understand the difference in size distribution for nano dicarboxylic acids formed during the clear-air, high-pollution and agricultural waste-burning periods. The correlation between size distribution and photochemical environment for dicarboxylic acid aerosol of various pollution origins will be studied and finally, pollution sources of atmospheric aerosols during the high-pollution and the agricultural waste-burning periods will be investigated.
|Appears in Collections:||[環境工程與科學系(所)] 國科會計畫|
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