| 摘要: | 本研究著重於有機揮發性污染物(Volatile Organic Compounds; VOCs) 自動化氣相層析系統的開發與運用。共分為兩部分，第一部分描述一系列 二維氣相層析技術的創新發展。第二部份則實際運用層析系統於野地量測 氣態有機物質並剖析排放特徵、臭氧生成機制與氣團傳輸的證據等關鍵空 污議題。 為了達到量測全範圍VOCs (C2~C12)之目的，本研究以丁氏切換器 (Deans switch)為核心，開發出一系列創新二維技術，如雙管柱單一偵檢器 二維氣相層析系統。系統只需單一吸附管與單一火焰離子偵測器(Flame Ionization Detector; FID)，結合電子壓力控制器(Electronic Pressure Controller; EPC)與丁式切換器精密控制載流氣體在兩管柱的流向與流速， 可任意控制流析物的滯留時間，將由雙管柱流析出之層析峰相互穿插再合 而為一，匯入單一FID，在此稱之為「層析剪裁技術」。 延續上述技術為基礎，採匯流後再分流連接方式，以一FID 與一電子捕 獲偵測器(Electron Capture Detector; ECD)同時偵測空氣中VOCs 與氟氯 碳化物(chlorofluorocarbons; CFCs)；再者並將在大氣中濃度極為穩定的物 種CFC-113 作為分析之「自身內標」，取代外標用以確保VOCs 分析品質。 此丁氏切換器被發現可作為「可調式分流器」(adjustable splitter)，且 可以EPC 微調輔助氣流，可將分析物以任何比例在兩管柱間分配。在此ㄧ概念下使用兩不同性質之靜相，例如DB-1 和Cyclodex-B，可成功地解析 空氣中芳香烴之結構異構物。 研究的第二部份則以二維氣相層析系統，實地在中國珠三角洲進行臭氧 前趨物量測計劃與數據探討。此外又以台灣地區光化學測站網 (Photochemical Assessment Monitoring Stations; PAMS)資料剖析中部地 區之高臭氧成因。 於2004 年秋季之珠三角連續監測顯示，車輛尾氣為廣州市區之主要臭 氧前趨物質來源，使用「主成分分析」(Principle Component Analysis)及 運用ethylbenzene/m/p-xylene 比值作為氣團老化指標可明顯地發現新墾地 區的氣團為經過長時間光化學反應後之老化氣團，成功的解釋珠江三角洲 出海口地區之高臭氧成因。 在PAMS 資料部份，利用兩物質同源但活性大小互異的特性，建立光 化指標，用於指示竹山地區氣團老化程度與臭氧濃度高低間的關係，並利 用中部地區PAMS 資料剖析南投地區高臭氧事件的原因。結合逆溫儀資 料，探討垂直混合層高度的變化對於VOCs 物種濃度的影響。經由主成分 分析與聚類分析「Cluster Analysis」區分VOC 排放源與其比例。並且將 VOC 長期數據進行趨勢分析，探討各物種的日夜、季節與多年長期濃度趨 勢變化。 The objective of this research is to develop novel automated gas chromatographic (GC) systems aiming at performing unattended analysis of volatile organic compounds (VOCs). The content comprises of two parts. The first part describes a series of innovated heart-cut GC techniques, which stem from the applications of the Deans switch. The second part addresses the actual employment of the developed GC system in the field. To measure the full range of VOCs from C2 to C12 and to increase the versatility of the system, the Deans switch was adopted as the core for developing a series of 2-D heart-cut techniques. Methods were developed to add now roles for the Deans switch in 2-D GC applications. In one design, the Deans switch was controlled in a manner to temporary hold-up fluents in the pre-column and, thus, allowed peaks to emerge in the desired retention windows. As a result, peaks from two columns of a Deans switch can be merged into a single flame ionization detector (FID) without overlapping. This concept is termed ?§peak tailoring??. In the second design, dual detectors were connected to the forth-mentioned system. Two types of compounds, i.e., VOCs and halocarbons, can be measured simultaneously by FID and electron capture detection (ECD), respectively. The most prominent merit arising from this configuration is to exploit atmospheric CFC-113, whose concentration has been proven steady in the atmosphere, as the ?§intrinsic?? to validate the stability of the continuous measurements. In the third desing, the Deans switch was developed into an adjustable splitter. This device splits the fluents to any desired ratio between two columns at any desired only via the adjustment of the auxillary flow. Under this concept, two columns of different phases, i.e., DB-1 and Cyclodex?VB columns, were adopted to successfully resolve the structural isomers of some mono-aromatics. The second part of the thesis addresses the characteristics of ambient VOCs and the ozone formation mechanism in the Pearl River Delta (PRD), China based on a measurement campaign. Discussion will then focus on the relationship between ozne and VOCs based on the observation from the Photochemical Assessment Monitoring Station (PAMS) in central Taiwan. Results from the PRD campaign revealed that vehicular exhaust is the main source of VOCs in Guangzhou. Using the ratio of ethylbenzene to m,p-xlene as an effective age indicator, it is found that the air in Xinken is substantially photochemically processed than that in Guangzhou, consistent with the less alkenes found in Xinken than in Guangzhou. The consistency in time and amplitude between the peaks of ozone and age indicator provides a strong evidence to tie ozone to photochemistry of VOCs in the downwind area of PRD. Data from PAMS in central Taiwan revealed that high correlation between ozone and the ratios of ethylbenzene to m,p-xlene was found. The aging concept was then usd to explain the high ozone phenomena in downwind areas of central Taiwan. Principal component analysis (PCA) and cluster analysis were also employed to classify sources and their contribution to the observed VOC species and their abundance. Motor vehicular exhaust was found to be the main contributor of ozone formation in this area. |
