|DC.description||National Central University||en_US|
|dc.description.abstract||每年春季中南半島北部生質燃燒旺盛，生質燃燒煙團經盛行西風傳送，分布廣泛遍及中南半島及東亞，影響這個區域對太陽輻射的收支。本文在泰國清邁(海拔1,396 m)、台灣鹿林山(海拔2,862 m)、台灣東沙島進行氣膠觀測，發現傳送至東沙島的氣流屬於地面傳輸，傳送至泰國清邁及鹿林山則屬於高層大氣傳送，在這三個地點觀測氣膠能分別瞭解受到高層大氣及地面傳送不同氣流來源影響的氣膠特性差異。
鹿林山春季受到盛行西風影響，是一個適合觀察中南半島生質燃燒氣團長程傳輸的地點。本文比較鹿林山與清邁源氣膠特性，發現生質燃燒氣膠經過傳輸以後，氣膠鉀離子增加4.4倍、硝酸根離子增加2.3倍、OC3 增加2.7倍、EC1-OP增加4.7倍、左旋葡萄糖增加3.4倍。本文也利用一些氣膠氧化特性指標來探討生質燃燒氣膠傳輸老化的現象，其中以WSOC/WIOC (水不可溶有機碳)最能突顯老化特性，WSOC在傳輸前後會由易揮發的有機碳物種組成轉變至不易揮發的有機碳物種，nss-SO42-/nss-K+及SOR (sulfur oxidation ratio)則會受到氣團經過中國南方的影響，使氣團nss-SO42-平衡狀態改變，在評估老化現象需特別注意。
|dc.description.abstract||Biomass burning (BB) is active in the northern part of Indochina Peninsula every spring. The BB plume transported by the prevailing westerly wind affects solar radiation budget in the Indochina Peninsula and East Asia. This study observed atmospheric aerosols at Chiangmai (1,396 m a.s.l., Thailand), Mt. Lulin (2,862 m a.s.l.), and the Dongsha Island. Trajectory analysis showed that the airmasses were transported near the surface at the Dongsha Island in contrast to the upper atmospheric transport at the Chiangmai and Mt. Lulin sites. The distinction of transported aerosol properties between surface and upper atmosphere can be appreciated at these three sites.
The Chiangmai site locates in the borderline of Thailand and Myanmar and is very close to BB source area in the Indochina Peninsula. Filter-based PM10 and PM2.5 samples were manually collected and analyzed for their chemical compositions. The result showed that Chiangmai aerosol mass was dominated by PM2.5 and sulfate and potassium ions were the major species in the water-soluble ions. OC3 and EC1-OP were predominant in aerosol carbonaceous fractions and 62% of organic carbon (OC) was in water-soluble organic carbon (WSOC). Oxalic acid was dominated in diacides and levoglucosan is undoubtedly the paramount fraction of anhydrous monosaccharide. The analyzed samples clearly reveal aerosol characteristics in the BB source area. The collected PM2.5 could be attributed to forest open-burning and most burnt tree species was softwood through the calculations of appropriate aerosol composition ratios.
Mt. Lulin is an appropriate site for observing BB plume transported from Indochina peninsula as it is located downstream of the prevailing westerly wind. This study compared aerosol characteristics between Mt. Lulin and Chiangmai and found that aerosol potassium ion increased 440%, nitrate ion increased 230%, OC3 increased 270%, EC1-OP increased 470%, and levoglucosan increased 340% in the BB plume during transport.
A few aerosol oxidation indices were employed to assess aging effect of biomass burning plume after transport. Among the selected indices, WSOC/WIOC (the ratio of WSOC over water-insoluble organic carbon) is the most significant index in showing transported aging aerosol. A conversion of more volatile to less volatile organics is noticed for WSOC. Note that the change of the equilibrium state of nss-SO42- influenced by the passage of airmasses through southern China makes nss-SO42-/nss-K+ and SOR (sulfur oxidation ratio) less effective in studying aerosol aging effect.
There are four cloud events observed in the state of before, during, and after periods in this study. Aerosol was brought by the airflow to the Mt. Lulin site for three events. PM1 concentration was likely to increase by the introduction of higher aerosol mass airflow after cloud event. In the activation efficiency of aerosol component in cloud, nitrate ion is activated easiest in the cloud followed by sulfate ion and ammonium ion is the least activated one.
The Dongsha Island is located in the northern tip in South China Sea. Its location makes it either affected by gaseous pollutants brought by Asian continental airmasses or minor anthropogenic pollutants when the airmasses are with oceanic origin.
In studying aerosol neutralization and compound form, ammonia deficiency is found for all at the three sites. The compound form of NH4+ and nss-SO42- at the Chiangmai site is (NH4)3(H)(SO4)2, while (NH4)2SO4 is inferred at the Mt. Lulin site. By adopting the “Chlorine Loss” mechanism to account for the reaction of sea-spray aerosol between acidic and basic gases, the inferred compound forms of NH4+ and nss-SO42- at the Dongsha Island are NH4HSO4 for PM10 and (NH4)3(H)(SO4)2 for PM2.5, respectively.
|DC.subject||Aerosol in South China Sea||en_US|
|DC.subject||aerosol aging indices||en_US|
|DC.subject||Southeast Asian aerosol||en_US|
|DC.subject||Biomass burning aerosol||en_US|
|DC.subject||Source characteristics of aerosol||en_US|
|DC.title||Near-source characterization of biomass burning aerosols and transport evolution from Indochina peninsula and aerosol properties at Dongsha island.||en_US|
|DC.publisher||National Central University||en_US|