An analytic study of the relationship between ozone and VOCs in Taipei metropolis

本研究於台北都會區下風處之ㄧ的汐止地區，應用移動式監測車觀測臭氧前驅物中56種VOCs的濃度，藉由相關性分析篩選出合適的光化指標，並配合氣象因子分析、污染物濃度分析與MIR理論，探討臭氧濃度變化趨勢與高臭氧時段主要貢獻臭氧生成的物種。 三次觀測實驗中以第一次觀測時段的氣象條件最適合光化反應進行，風向的不同反映在污染物濃度的變化上，西風時污染物來源應以台北都會區為主，NO、NO2與VOCs等污染物濃度的變化較大且臭氧濃度較高；東風時污染物則主要經基隆河河谷傳輸而至，各污染物濃度變化相對較小。相關性分析所篩選出的光化指標中m,p-Xylene / Ethylbenzene、o-Xylene / Ethylbenzene與1,2,4-Trimethylbenzene / n-Propylbenzene皆可迅速反映出交通尖峰與光化反應前後比值的變化。以m,p-Xylene / Ethylbenzene為例，其比值在西風時介於0.8至2.4；東風時其比值則介於0.8至1.4，顯示光化指標因污染物來源與光化程度不同而有所差異，且與臭氧濃度有相當之關聯性。 高臭氧濃度時段中，若以光化反應前後消耗的VOCs濃度配合MIR估算可生成之最大臭氧濃度，並與以光化反應前的VOCs濃度估算之臭氧生成潛勢相比。可知11月5日與6日所消耗的VOCs可生成之臭氧濃度分別為192.5 ppb與105.7 ppb，而光化反應前該時段之臭氧生成潛勢為712.4 ppb。可知以消耗量估算臭氧生成潛勢比較接近臭氧實際觀測值132 ppb與97 ppb。其中烯類分別佔整體約40.7 %與33.5 %，芳香烴類則為45.9 %與45.1 %。解析臭氧貢獻前十名物種則佔整體約78 %，其中以m,p-Xylene、Isoprene與Toluene較高。This study observed the concentration of 56 VOCs of ozone precursors by using mobile laboratory in Sijhih, which has been one of the leeward areas of Taipei city, and then photochemical indicators are sifted by correlation regression analysis. It would also cooperate with meteorological factors, pollutant concentration analysis and MIR theory to discuss the variation tendency of ozone concentration and main contribution species during high ozone concentration period. In the three observing experiments, the meteorological conditions of the first set were the most suitable for photochemical reactions in atmosphere. Moreover, the variation of wind direction was reflected on the change of pollutant’s concentration. By west wind, the sources of pollutants were mostly from Taipei city. A larger variation of NO, NO2 and VOCs concentrations, and higher ozone concentration were observed; By east wind, the pollutants were transported through Keelung river and the variation of the pollutants were less related. The photochemical indicators, including m,p-Xylene / Ethylbenzene, o-Xylene / Ethylbenzene and 1,2,4-Trimethylbenzene / n-Propylbenzene, were filtered by correlation regression analysis. They reflected the relationship between rush hour and the change of ratio after photochemical reactions. For example, the ratio of m,p-Xylene and Ethylbenzene was in the range of 0.8 to 2.4 for west wind direction and 0.8 to 1.4 for east wind direction. The results indicated that the photochemical indicators and the level of photochemical reactions are strongly correlated with the sources of pollutants, especially for ozone concentration. During the high ozone concentration period, it would be compared with the ozone formation potential to estimate the largest ozone concentration by the consumed VOCs. The consumed VOCs, including 40.7% and 33.5% alkenes, aromatics account for 45.9% and 45.1%, would be produced about 192.5 ppb and 105.7 ppb in November 5 and 6. The results were nearer to the 132 ppb and 105.7 ppb observed than the 712.4 ppb before photochemical reactions were. In addition, the top ten main compounds were engaged about 78% of total ozone formation potentials, and the main three compounds were m,p-Xylene, Isoprene, and Toluene.第一章 前言 1 1.1 研究緣起 1 1.2 研究目標 4 第二章 文獻回顧 5 2.1對流層中的臭氧 5 2.1.1 對流層中的臭氧的來源 5 2.1.2 臭氧的生成與反應機制 6 2.1.3 全球各地臭氧變化趨勢 8 2.1.4 台灣地區的臭氧問題 9 2.2 臭氧前驅物-VOCs之特性 12 2.2.1 VOCs/NOx比例 13 2.2.2 VOCs之反應性 13 2.2.3 生物源VOCs 14 2.2.4 光化反應生命週期 15 2.2.5 氣象擴散速率以及下風距離 15 2.3 VOCs物種觀測於光化學分析之應用 16 2.3.1 光化學監測站 16 2.3.2 移動式監測站 17 2.3.3 光化指標理論 19 2.3.4 光化指標的建立與應用 19 2.3.5 VOCs光化反應性尺度 21 第三章 研究方法 23 3.1 研究規劃 23 3.2 特定VOCs物種觀測 27 3.2.1目標區域選定 27 3.2.2 VOCs監測車 29 3.2.3 配置56種VOCs物種檢量線 30 3.2.4 觀測時段選定 31 3.2.5 VOCs自動監測參數設定 33 3.3 光化指標分析 36 3.3.1 VOCs物種間相關性分析 36 3.3.2 光化指標與臭氧濃度之時間序列分析 38 3.4 臭氧生成潛勢分析 41 3.4.1 VOCs物種濃度分析 41 3.4.2 VOCs物種臭氧生成潛勢分析 42 3.4.3 高臭氧濃度時段之貢獻物種分析 42 第四章 結果與討論 45 4.1 氣象因子與污染物濃度分析 45 4.1.1 第一次觀測實驗 46 4.1.2 第二次觀測實驗 57 4.1.3 第三次觀測實驗 65 4.2 光化指標分析 75 4.2.1 VOCs物種間相關性分析 75 4.2.2 第一次觀測實驗光化指標與臭氧濃度之時間序列分析 86 4.2.3 第二次觀測實驗光化指標與臭氧濃度之時間序列分析 105 4.2.4 第三次觀測實驗光化指標與臭氧濃度之時間序列分析 109 4.3 臭氧生成潛勢分析 113 4.3.1 VOCs物種濃度分析 113 4.3.2 VOCs物種臭氧生成潛勢分析 117 4.3.3 高臭氧濃度時段貢獻物種分析 121 第五章 結論與建議 127 5.1 結論 127 5.2 建議 131 參考文獻 132 附 錄 138 附錄一 VOCs物種濃度資料 139 附錄二 光化指標組合相關性分析結果 15