| 摘要: | 依據美國空氣清淨法 (Clean Air Act Amendments, CAAA)，有害空氣污染物 (Hazardous Air Pollutants, HAPs)定義為「任何空氣污染物導致癌症或其他對健康危害很大之症狀，稱為有害空氣污染物」。目前美國環保署共建立了189種HAPs物種資料，當中包含揮發性有機化合物 (Volatile Organic Compounds, VOCs)、重金屬、酸氣和多環芳香烴等物種。台灣環保署則是在西元2017年公告了固定污染源有害空氣污染物排放標準草案，共有72個物種將在未來分三階段進行管制。
在我國環保署公告之72個HAPs中，大部分揮發性有機物質皆可被美國環保署TO-14A、TO-15方法，或是台灣環保署環檢所公告之NIEA A715.15B方法所分析，但這三種方法皆為離線式 (Off-line)分析方法，需將現場空氣透過採樣罐採樣後帶回實驗室後，再使用氣相層析質譜儀 (Gas Chromatography/Mass Spectrometer)分析。然而採樣罐法因為無法得到及時的連續數據，故不易捕捉到現場瞬間的濃度高低變化，以反映出排放源或氣象影響的特性，故本研究結合前濃縮熱脫附系統 (Thermal Desorption, TD)並串聯氣相層析質譜儀 (TD-GC-MS)，開發在線 (On-line)監測方法。
在TD系統中為了因應台灣空氣中偏高的相對濕度，亦將除水模組加入用以解決連續監測時會遇到的高水氣問題，以降低TD-GC-MS受到大量水氣而受損的影響。實驗時以TO-14A標準氣體作為測試本方法之分析氣體，比較乾燥樣品和加濕樣品在結果上之差異，以檢視分析物是否會受到除水影響，結果以再現性和檢量線線性來表現。本實驗室將完整的TD-GC-MS系統架設在中部某工業區東北方約八公里遠處，於7月3日時開始以每小時一筆數據連續監測HAPs物種，在現場我們發現了微量的HAPs物種，例如苯、甲苯、乙苯和1,1,2,2-四氯乙烷，目前實地監測仍然持續進行中。
當使用NIEA A723.73B的方法測量半導體廠的酸排放管道中的非甲烷總碳氫化合物 (NMHC)時，本研究所使用之TD-GC-MS系統亦可用於未知物之定性。此未知訊號被視為透過酸排放管道非法排放出的VOCs，因此本實驗室受到半導體廠委託來調查此爭議。將該半導體廠酸排放管道之氣體採樣後透過TD-GC-MS系統進行分析，成功的確認此未知物為C4F8。C4F8為半導體行業使用的乾蝕刻氣體，並不應被視為NMHC或VOCs，故可確認NIEA A723.73B的訊號為C4F8干擾所造成之誤差。;According to the Clean Air Act Amendments (CAAA) of the United States, Hazardous Air Pollutants (HAPs) are those known to cause cancer and other serious health impacts. The US Environmental Protection Agency has established a total of 189 species of HAPs, including Volatile Organic Compounds (VOCs), heavy metals, acid gases, and polycyclic aromatic hydrocarbons. The Taiwan Environmental Protection Agency announced the emission of hazardous air pollutants from stationary source in 2017. A total of 72 species will be regulated in three stages in the future.
Among the HAPs regulated by the Taiwan Environmental Protection Agency, the U.S. EPA method TO-14A and TO-15, or the NIEA A715.15B method of the Environmental Protection Agency of the Taiwan have conducted analysis. These methods are all off-line analysis. The on-site air samples must be sampled from canister and brought back to the laboratory before being analyzed by Gas Chromatography/Mass Spectrometer. However, this method is not easy to capture the instantaneous concentration surges to link to emissions. In this study, a pre-concentrated thermal desorption system (TD) combined with gas chromatography mass spectrometry (TD-GC-MS) was developed to monitor ambient HAPs on-line. To cope with the high air humidity, the TD system was added with a water removal unit prior to the sorbent trap to reduce water interference in the sample pre-concentration stage and mass spectrometry. The TO-14A standard gas was used to assess reproducibility and linearity of both dried and humidified samples for comparison. The completed system of TD-GC-MS was deployed approximately 8 km northeast of an industrial complex to begin continuous measurements of HAPs on July 3 with hourly resolution. The measurements are still undergoing as this thesis is wrapping up. We found trace amounts of the four HAPs, e.g., benzene, toluene, ethylbenzene and 1, 1, 2, 2 – tetrachloroethane at the site.
The system of TD-GC-MS was also applied to the investigation of an unknown signal when measuring air in acid ventilation of a semiconductor plant using the method of NIEA A723.73B. Thus, the source of the signal was deemed unlawful release of VOCs through the acid gas ventilation, which had been denied by the plant authorities. Our laboratory was invited by the plant authority to investigate this dispute. Analysis by TD-GC-MS from samples collected from the plant has successfully identified this unknown compound as C4F8, which is an etching gas used in this industry. C4F8 should not be deemed a non-methane hydrocarbon (NMHC) or a VOC and; thus, the signal reported by NIEA A723.73B should be a false positive error. |
