甲烷作為重要的溫室氣體之一，對於地球暖化具有顯著貢獻。全球及台灣的觀測資料皆顯示甲烷濃度逐年上升，並且在近年來有較大幅度的成長率。目前關於台灣甲烷特性的研究相對有限，對於各行業的排放統計也未包含甲烷的排放估計，若能瞭解各場域的排放來源變化情形，能夠有效地制定減排策略及改善甲烷污染，並且對於台灣不同區域的甲烷污染特徵及差異能有更深入的理解。 為瞭解台灣的甲烷排放特性和各地區的污染來源，使用我國環保署空品站和背景站數據，探討台灣各區域甲烷的長期趨勢，及季節性等變化。進一步透過衛星資料分析東亞源區對於台灣的甲烷影響程度。最後利用光化站資料探討氣團老化程度，以分析各區域甲烷的可能來源特徵，並透過風場資料判斷高濃度事件主要的來源方向。 結果顯示，台灣各區域的甲烷濃度成長趨勢大致與背景站相同，並在2021年有顯著成長率。各區域季節及日夜變化與全球趨勢相同均為冬春季高；夏季最低，0-5時最高；中午最低。季節振盪在三月份時較高，透過衛星資料分析結果，顯示東亞源區對於台灣及鄰近地區甲烷具有貢獻。都會區受到日夜間交通及工業排放貢獻差異導致日夜震盪幅度小於工業區。都會區甲烷與VOCs相關性較好，顯示兩者來源的一致性較高，光化指標結果顯示高濃度甲烷皆發生在較為老化的氣團，說明都會區甲烷受到區域性排放的影響較大。工業區交通排放相對都會區較不顯著，與VOCs相關性較差，污染來源較不一致，光化指標顯示工業區高濃度甲烷來源較複雜，本地及區域性排放分別主導不同工業區的甲烷來源。 ;Methane, as one of the greenhouse gases, plays an important role in global warming. Observational data from both global and Taiwan sources have shown a steady increase in methane concentration over the years, with more substantial growth rates in recent times. Currently, research on the characteristics of methane in Taiwan is relatively limited. Understanding the variations in emission sources in different fields can effectively guide emission reduction strategies and improve the pollution of methane. To gain insight into Taiwan′s methane emission characteristics and pollution sources in different regions, we utilized data from EPA stations and NOAA’s background stations to explore the long-term trends and seasonal variations of methane in Taiwan. Additionally, we analyzed satellite data to assess the impact of East Asian source regions on methane concentration in Taiwan. Furthermore, using PAMS data, we examined air mass aging levels to identify potential characteristics of methane sources in different regions and used wind field data to determine the main directions of high-concentration events. The results indicate that methane concentration in different regions of Taiwan has exhibited similar growth trends as background stations, with a significant increase observed in 2021. The seasonal variations in all regions follow a pattern of higher methane concentration in winter and spring, and lower in summer. The diurnal variations of methane worsen at midnight. The seasonal oscillations are more pronounced in March. Satellite data revealed a contribution of East Asian source regions to methane levels in Taiwan and its neighboring areas. The metropolitan area exhibited smaller diurnal variations due to differing contributions from traffic and natural gas. A better correlation between methane and VOCs in the metropolitan area suggests a higher consistency in their sources. The non-methane hydrocarbon (NMHC) ratios pointed out that high methane concentrations occur in aged air masses, indicating a greater influence of regional emissions on methane levels in the metropolitan area. In contrast, industrial areas exhibited a worse correlation with traffic emissions, showing more diverse pollution sources. The NMHC ratios suggested that high methane concentrations in industrial areas are derived from both local and regional emissions. In summary, this study provides valuable insights into the characteristics of methane emissions in Taiwan and sheds light on the pollution sources in different regions. The findings contribute to the formulation of effective emission reduction strategies and the improvement of methane pollution.
