| 摘要: | 生質燃燒、石化業燃燒及交通污染是有機氣膠(organic aerosol)及碳黑(soot)的重要初始污染源，也可再藉由光化反應形成二次有機氣膠污染，這些有機氣膠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，已有證據指出因有機氣膠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。然而目前對於微粒有機物種的形成及微粒粒徑分布的相關研究，國內外尚少瞭解，尤其是高污染及農廢燃燒時期與長程傳輸及偶發的沙塵暴侵襲事件與春季疑似中南半島大規模生質燃燒等污染發生時之5-100 nm 的奈米氣膠及粒徑至18 μm 的氣膠有機物種分布特性的研究尚有很大探討空間，乃至於乾淨大氣的奈米有機物種特性亦尚未深入瞭解。因此，本研究將以三年時間(99 年8 月－102 年7 月)，探討南台灣地表背景大氣環境(第一年)( (99 年8 月－100 年7 月)、南部郊區乾淨大氣時期(第二年) (100 年8 月－ 101 年7 月)及不同大氣污染時期(第三年) (101 年8 月－102 年7 月)之奈米/微米(5nm- 18μm)氣膠有機物種特性，同時同步採集包括酸鹼氣體、PM2.5、PM10 之粗細微粒，鑑別大氣氣膠中包括有機酸、脫水醣類、醣醇類的特徵物種，搭配水溶性無機陰陽離子組成，藉此可探討奈米有機物種之初始粒徑生成變異，討論微粒之nuclei mode (5-100 nm)、condensation mode (0.10-0.54 μm)、droplet mode (0.54-2.5 μm)及coarse mode (2.5-18 μm)的有機物種之間之關聯性，並探討地表背景及南台灣郊區之不同污染時期的 potassium to levoglucosan (K/Levo), levoglucosan to mannosan (Levo/Manno), levoglucosan to xylitol (Levo/Xylitol)，及有機酸與無機鹽光化強度特徵的oxalic acid to sulfate (OX/Sulfate)與光化生成及交通污染排放貢獻參數的malonic acid to succinic acid (M/S)，以做為判斷大氣氣膠污染貢獻指標及有機氣膠光化機制之瞭解，最後以高斯軌跡傳遞係數模式(GTx)解析主要污染源的污染貢獻分配。
Organic aerosol and soot, which originate from biomass burning, traffic emissions, 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 organic aerosol 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 organic aerosol 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 organic aerosol in the clean atmosphere have not been studied in-depth. Hence, this three-year research will investigate aerosol characteristics and contribution distribution to aerosol of nano/micron organic compounds, including carboxylic acids, anhydrosugars, sugar alcohols with inorganic species during periods of various atmospheric pollutions. Formation variations of the organic aerosols, correlations among organic species and their various pollution sources will also be studied in this research. The gaseous pollutants, PM10, PM2.5 will be collected at the same periods. We discuss the chemical properties of nuclei mode (5-100 nm), condensation mode (0.10-0.54 μm), droplet mode (0.54-2.5 μm) and coarse mode (2.5-18 μm) in organic aerosol. In addition, the indicator ratios of potassium to levoglucosan (K/Levo), levoglucosan to mannosan (Levo/Manno), levoglucosan to xylitol (Levo/Xylitol) will be judged to demonstrate the various pollution sources. The first year (Aug. 2010－July 2011) will be devoted to studying the long-term background atmospheric organic aerosol particles nano up to 18 μm at Kenting National Park and their formation variations. The second-year research (Aug. 2011－July 2012) will study the long-term size variations of nano up to 18 μm organic 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 organic aerosol characteristics as collected during the first year and the characteristic difference and sources of organic aerosol 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. 2012－July 2013) will include investigating the formation characteristics of nano/micron organic aerosol during various PM episodes. Additionally, the information accumulated during the three-year study period will be analyzed to study the characteristics of nano/micron organic aerosol observed during various PM episodes in order to understand the difference in size distribution for nano/micron organic compounds formed during the clear-air and PM episodes. Furthermore, the use of GTx Model for simulating the conversion between the background organic aerosol and inorganic salts and performing sensitivity analyses. The correlation between size distribution and photochemical environment for organic aerosol of various pollution origins will be studied and finally, pollution sources of atmospheric aerosols during various PM episodes will be investigated. |
