破壞臭氧層物質－氟氯碳化物（CFCs）－之監測與排放行為

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題名:	破壞臭氧層物質－氟氯碳化物（CFCs）－之監測與排放行為
作者:	徐誠昱;Hsu, Cheng-Yu
貢獻者:	化學學系
關鍵詞:	氟氯碳化物;線上連續監測 GC-ECD;自製 DW-TD/GC/ECD;Chlorofluorocarbons;Online GC-ECD;custom-built DW-TD/GC/ECD
日期:	2025-07-08
上傳時間:	2025-10-17 11:15:57 (UTC+8)
出版者:	國立中央大學
摘要:	氟氯碳化物（Chlorofluorocarbons，CFCs）因具有極為穩定的化學性質，經排放後會逐漸擴散至高空破壞平流層臭氧，藉由蒙特婁議定書在過去 30 年間的積極落實已使 CFCs 完全被停止生產與使用，目前 CFCs 排放源已大致消失，在大氣中濃度也已因充分混合均勻而呈現固定背景濃度，且濃度的下降極為緩慢。為了查驗我國CFCs是否仍存在不正常排放，本實驗室研發了一套除水（Dewater Unit，DW）及熱脫附儀（Thermal Desorption，TD）串接一氣相層析儀-電子捕獲偵測器（GC/ECD）設備進行線上監測，以了解國內環境中 CFCs 排放狀態；其與以往實驗室常見搭載的偵測器截然不同，藉此發展出更新穎的 CFCs 物種背景值濃度監測方式。在此 DW-TD 串接 GC/ECD 方法中，每小時可同時監測四種鹵碳化合物：CCl2CF2（CFC-12）、CCl3F（CFC-11）、CClF2CCl2F（CFC-113）、CCl4。本實驗利用標準氣體校正工作標準氣體（以乾淨背景空氣壓縮製成）的濃度，再藉由變化工作標準氣體進樣體積建立五點檢量線，R2 值> 0.995。而後將此設備搬至新竹科學園區，並於 2024 年 3 月進行十三天的連續監測，監測期間每日查核數據為使用 34.0 L 大型不鏽鋼瓶中的查核氣體(於中央大學周遭農田湖邊採集的空氣)，在十三天的分析期間內十三筆數據的再現性 RSD = 0.03%~0.37%，顯示出 DW-TD 串接 GC/ECD 之高度穩定性。在監測工作中發現 CFC-12 所有數據點（> 250筆）均極為平穩（~485.2 ppt ± 0.22%），而 CFC-11，CFC-113 與 CCl4 卻發現不如 CFC-12 平穩而出現明顯排放特徵，其中以 CFC-11 最為明顯。為了和新竹科學園區的工業特性區域做一個對照，在 2024 年 5 月又於具商業特性區域的臺灣大學進行一個月相同方式的監測（> 570筆），測出極為穩定的 CFCs 背景值，RSD 為 CFC-12 = 0.05%、CFC-11 = 0.10%、CFC-113 = 0.32% 和 CCl4 = 0.29%，因此說明在臺灣大學並未監測到 CFCs 物質的排放，相較之下，新竹科學園區有不正常的 CFCs 物質排放，表示 CFCs 的排放行為在工業界可能仍然存在。由高值事件再結合後推軌跡追蹤發現排放可能來自於測站南方之某半導體廠，推測可能為舊式冷氣設備冷媒洩漏，或是電漿式處理設備在去除全氟化合物（Perfluorinated compounds，PFCs）過程中意外產生，均屬破壞環境之行為，不利於臭氧層修復與加劇全球暖化現象。藉由 DW-TD 串接 GC/ECD 的監測結果不但觀察到 CFC-12（涵蓋舊款車輛與冷氣機冷媒）之使用在臺灣某些商業及工業特性區域已被成功廢除，同時亦間接襯托出其他 CFCs 在新竹科學園區仍有排放特徵，此發現有賴於性能優異之 DW-TD 串接 GC/ECD，尤其是自製 DW-TD 在進樣與濃縮上之高穩定性表現。 ;Chlorofluorocarbons (CFCs), owing to their exceptionally stable chemical properties, gradually diffuse into the upper atmosphere after being emitted, where they contribute to the depletion of stratospheric ozone. Over the past 30 years, the effective implementation of the Montreal Protocol has led to the complete cessation of CFC production and use. As a result, most emission sources have been eliminated, and the atmospheric concentrations of CFCs have become well-mixed, exhibiting stable background levels with a very slow rate of decline. To investigate whether abnormal CFC emissions still occur in Taiwan, our laboratory developed an online monitoring system consisting of a Dewater Unit (DW), a Thermal Desorption unit (TD), and a Gas Chromatograph equipped with an Electron Capture Detector (GC/ECD) to assess ambient CFC levels. Unlike conventional detectors commonly used in laboratories, this configuration allows for a more advanced approach to monitoring the background concentrations of individual CFC species. A custom-built DW-TD/GC/ECD system was employed for automatic air sampling and analysis in this study. A crucial step in the analytical procedure involved removing residual oxygen from the sample and system using dry nitrogen, as the presence of oxygen may saturate the ECD signal and interfere with CFC chromatographic peaks. This method enabled hourly online monitoring of four halocarbons: CCl₂F₂ (CFC-12), CCl₃F (CFC-11), CClF₂CCl₂F (CFC-113), and CCl₄. A clean background air standard was used to construct a five-point calibration curve by varying the injection volume, achieving coefficients of determination (R²) greater than 0.995. The concentrations were then calibrated against the standard gas. The system was deployed at the Hsinchu Science Park in March 2024 for continuous monitoring over a 13-day period. During the monitoring period, daily data validation was conducted using a reference air sample collected from a lakeside location near agricultural fields surrounding National Central University and stored in a 34.0 L stainless steel canister. Over the 13-day period, thirteen measurements yielded relative standard deviations (RSDs) ranging from 0.03% to 0.37%, indicating the high stability of the DW-TD/GC/ECD system. Among the four target compounds, CFC-12 exhibited a highly stable concentration (~485.2 ppt ± 0.22%), whereas CFC-11, CFC-113, and CCl₄ showed noticeable emission characteristics, with CFC-11 being the most prominent. For comparison, the same monitoring campaign was conducted at National Taiwan University in May 2024, collecting over 570 samples. The results showed stable background concentrations, with RSDs of 0.05% for CFC-12, 0.10% for CFC-11, 0.32% for CFC-113, and 0.29% for CCl₄, confirming the absence of detectable CFC emissions in Taipei City. In contrast, the abnormal levels observed at Hsinchu Science Park suggest that the emissions likely originated from industrial activities. Backward trajectory analysis of elevated concentration events suggested that the emissions may have originated from a semiconductor facility located south of the monitoring site. Possible causes include leakage from outdated cooling systems or unintended formation during plasma treatment processes aimed at removing perfluorinated compounds (PFCs). Such emission behaviors are environmentally harmful, impeding ozone layer recovery and exacerbating global warming. The monitoring results obtained using the DW-TD/GC/ECD system confirm the successful phase-out of CFC-12 (previously used in air conditioners and automotive refrigerants), while simultaneously revealing fugitive emissions of other CFC species. These findings underscore the exceptional performance of the analytical setup, particularly the high stability and reproducibility of the self-developed DW-TD system in sample introduction and pre-concentration.
顯示於類別:	[化學研究所] 博碩士論文

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