Chemical characteristics of biomass burning aerosol in Viet Nam and in Taiwan

黎福華(LE PHUOC HOA)

指導教授 ： 張晃猷 ； 白光宇

國立清華大學/生命科學院/分子醫學研究所/碩士(2013年)

摘要

摘要
生質能是亞洲農村應用最廣泛的能源。燃燒包括木材、木炭及農業廢棄物等生質能可作為家庭燃料或達到農地整理之目的。然而生質燃燒排放的煙霧顆粒、一氧化碳、氮氧化物及碳氫化物對全球大氣能產生巨大的衝擊，特別是在熱帶及亞熱帶地區。因此全球科學家及決策者都密切關注生質燃燒造成的空氣汙染對人體健康及氣候變遷的影響。本篇論文評估越南和台灣生質燃燒產物的化學性質，比較兩地在水稻收割後燃燒農田對空氣品質的衝擊，並測定兩地空氣樣品中陰陽離子及生質燃燒產物或真菌追蹤物的醣類濃度，發現越南空氣樣品的離子濃度高於台灣樣品。另外利用搭配脈衝式安培偵測器的高效能陰離子交換層析儀(HPAEC-PAD)進行生質燃燒氣膠中聚醣同分異構物如左旋葡萄醣聚醣(levoglucosan)、甘露醣聚醣(mannosan)、半乳醣聚醣(galactosan)及真菌孢子追蹤物如阿拉伯醣醇(arabitol)、甘露醣醇(mannitol)的分析。結果顯示在生質燃燒的季節時，在越南的左旋葡萄醣聚醣濃度較在台灣的濃度為高。此外在越南生質燃燒季節裡，左旋葡萄醣聚醣/甘露醣聚醣比值呈現高度相關性(Son La 比值為21.2，Da Nang比值為20.6-45.2)，清楚地指出稻草是主要生質燃燒的燃料類型。同樣地，越南採樣檢體有機碳和元素碳的濃度也是遠高於台灣，然而在2012年生質燃燒季節越南樣品有機碳和元素碳的比值卻相對低於台灣樣品的比值。通常很高的有機碳和元素碳的比值意味著由生物來源或生質燃燒活動帶來的重大的影響。在越南採得樣本的真菌追蹤物如阿拉伯醣醇與甘露醣醇都高於台灣的樣品。除此之外，我們發現在真菌追蹤物和生質燃燒追蹤物如左旋葡萄聚醣與鉀離子之間有顯著的相關性，證實這些化合物有共同的排放源，推測在Son La地區大量的真菌追蹤物可能和該區生質燃燒活動有關。本研究也是首次運用多種分子追蹤物分析廣大地區的氣膠粒子，觀測從東南亞生質燃燒排放的煙霧順著季風長途運輸，經由越南、中國南方、南海、對台灣造成的影響。

關鍵字

生質燃燒 ； 氣膠粒子 ； 真菌追蹤物

並列摘要

ABSTRACT
Biomass is widely used as energy source in rural households in Asia. Biomass burning comprises the incineration of wood, charcoal and agricultural waste as household fuel or in form of the combustion of crop residues on farm fields. Smoke emissions from biomass burning have a significant impact on global atmospheric chemistry, as they constitute a large source of particulate matter as well as carbon monoxide, nitrogen oxides, and hydrocarbons, especially in the tropics and subtropical regions. Therefore, biomass burning has attracted the attention of the general public, scientists and policy makers globally due to its contribution to air pollution and the effects of these emissions on human health and climate. This thesis evaluates the chemical characteristics of biomass burning aerosol in Vietnam and in Taiwan and investigates the impact of post-harvest burning of rice fields on the air quality in Taiwan and in Vietnam in comparison. Concentrations of inorganic anions and cations, as well as selected organic compounds, including molecular tracers for biomass burning (anhydrosugars) and fungi (sugar alcohols), were measured in air samples (both ambient air and near-source samples) from the two countries. Ion concentrations in air samples from Vietnam were higher than those in the Taiwan air samples. An analytical method based on high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was used to measure the isomeric anhydrosugars (levoglucosan, mannosan, and galactosan) as well as the fungal spore tracers (arabitol and mannitol) in the biomass combustion aerosol. Levoglucosan concentrations were observed during the biomass burning season in Vietnam at higher levels than in Taiwan air samples collected in the rice field burning season. In addition, the relatively high levoglucosan/mannosan ratios of 21.2 (Son La) and 20.6-45.2 (Da Nang) clearly indicated that rice straw was a major type of fuel that was burned in the biomass burning season in Vietnam. Likewise, organic carbon (OC) and elemental carbon (EC) concentrations in Vietnam were much higher than in Taiwan. However, the OC/EC ratios in Vietnam were relatively lower than those in Taiwan in the spring 2012 biomass burning season. A very high OC/EC ratio implies important influence from biogenic sources and/or biomass burning activities. The fungal tracer concentrations (arabitol and mannitol) in Vietnam were higher than those in Taiwan. In addition, statistically significant correlations were found between the simultaneously observed fungal tracers (arabitol and mannitol) and biomass burning tracers (levoglucosan and K+), suggesting that these species were emitted by co-located sources, and hence the elevated fungal tracers were likely associated with biomass burning activities at Son La, Vietnam. Furthermore, long-range transport of biomass burning smoke emissions from Southeast Asia (especially Vietnam) has been shown for the first time affecting downwind areas by smoke particle transport across the South China Sea to the sampling sites in Taiwan, under the influence of the prevalent monsoon winds, using molecular characteristics of the ambient aerosol particles in the source region and receptor sites.

並列關鍵字

Biomass burning ； HPAEC-PAD ； Anhydrosugars ； Sugar alcohols ； OC ； EC

參考文獻

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