| 摘要: | 本研究以質子轉移反應質譜儀(proton-transfer-reaction mass spectrometry, PTR-MS)為技術核心，建立一套空氣污染鑑識方法，應用於工業區空污問題診斷。透過其高時間解析、低偵測極限的優勢，搭配多成分觸發採樣技術，於污染物濃度高值當下觸發採樣，採集之樣本攜回實驗室以GC-MS/FID (gas chromatography-mass spectrometry/flame ionization detector)分析108種VOCs。本研究將使用兩種類型PTR-MS，包含四極柱(PTR-QMS)與飛行時間質譜儀(PTR-TOF/MS)，應用於鑑定工業區排放之揮發性有機化合物(volatile organic compounds, VOCs)。
本研究選定一處綜合型工業區(平鎮工業區)執行現地觀測，透過實場10天的污染物調查，建立工業區的排放物質清單。由排放清單之成分作為觸發對象，以PTR-QMS執行多成分觸發採樣，掌握周界物質具有濃度突發性高值之事件，並剖析事件當下之污染物組成。
平鎮工業區共採集18個事件樣本，經由GC-MS/FID的分析，工業區環境中以含氧之揮發性有機化合物(oxygenated volatile organic compounds, OVOCs)為主，其中包含acetone、butanone、methyl isobutyl ketone (MIBK)、methyl butyl ketone (MBK)、ethyl acetate、vinyl acetate、isopropanol、methyl tert-butyl ether (MTBE)等8種有機物質，占108種VOCs總量16% - 75%。由於OVOCs含量顯著的結果，將PTR-MS監測之OVOCs (GC-MS/FID無法分析之物種，例:乙醇、乙醛、醋酸等)與108種VOCs整併，結果顯示PTR-MS額外監測之OVOCs大幅提高OVOCs之權重比，占總量55% - 82%。
將平鎮工業區OVOCs高比例的含量結果與本實驗室先前研究成果比較，新竹工業區OVOCs占108種VOCs總濃度的15% - 60%；中壢工業區OVOCs占108種VOCs總濃度的32% - 84%，而台北都會區OVOCs則僅占108種VOCs總濃度的8% - 10%，顯示工業區大量OVOCs排放可能是造成異味事件與空氣品質不良的元兇之一。
此外，相較於台北都會區OVOCs中以methyl tert-butyl ether (MTBE)為主要成分，平鎮、新竹、中壢工業區的OVOCs中則以ethyl acetate、acetone、butanone、isopropanol等工業常用之有機溶劑為主。綜合此三處工業區的監測結果，整理出工業區周界環境中前十大污染物，其中以醛、酸及醯胺等物質最為特殊，這些偏極性的化學物質無法以傳統不鏽鋼採樣罐結合GC/MS法鑑定；再者因濃度偏低，也不易被其他方法(如FT-IR法)偵測或鑑定，而PTR-MS大幅補強以往對於這些關鍵物質鑑定能力的不足。
;This study is to develop a monitoring method involving the use of proton-transfer reaction mass spectrometry (PTR-MS) to investigate chemical pollutants released from industrial parks. Taking the advantages of the PTR-MS’s ultra-low detection limits and high temporal resolution, the trigger-sampling technique was coupled with PTR-QMS to capture plume events from the industrial parks. The triggered samples were then analyzed with in-laboratory GC/MS/FID (gas chromatography/mass spectrometry/flame ionization detector) for 108 volatile organic compounds (VOCs) to characterize the chemical compositions of the plume events. In this study, two types of mass spectrometry were involved: quadruple (called PTR-QMS) and time of flight (called PTR-ToF/MS).
This study demonstrated a 10-day field observation in Pingjhen Industrial Park for characteristic pollutants. By targeting selected VOCs characteristic of the Pingjhen Industrial Park, flask samples were collected in sequence when the PTR-QMS detected concentrations surpassing the pre-set trigger levels. Eighteen event samples were triggered as a result, and were analyzed by in-lab GC/MS/FID to reveal the composition of 108 VOCs. It was found that majority of the constituents was oxygenated VOCs (OVOCs), including acetone, butanone, methyl isobutyl ketone (MIBK), methyl butyl ketone (MBK), ethyl acetate, vinyl acetate, isopropanol and methyl tert-butyl ether (MTBE), accounting for 15% - 75% of the total 108 VOCs for the event samples. When including the compounds that were measured by PTR-MS but cannot be analyzed by GC/MS/FID (e.g., ethanol, acetaldehyde and acetic acid), the percentages of OVOCs increased to 55% - 82%.
Compared with our previous trigger-sampling studies, OVOCs accounted for 15% - 60% of the total 108 VOCs in Hsinchu, 32% - 84% in Chungli, but only 8% - 10% in the Taipei metropolitan area. Such large fractions of OVOCs in the vicinity of industrial park could explain the frequent odor complaints by the local residents.
Moreover, contrasting to the urban environment such as Taipei, where methyl tert-butyl ether (MTBE) was the major component of OVOCs, organic compounds commonly used in industry, such as ethyl acetate, acetone, butanone, isopropanol, etc., were the primary contributors to OVOCs from these industrial parks (e.g., Pingjhen, Hsinchu and Chungli). By summarizing the monitoring results of the three industrial parks, a list of top ten pollutants was established for each industrial park, on which aldehydes, acids and amides were the common ones worth noticing and more related to foul smells. Usually these polar compounds are not suitable to be sampled by flasks, and their recoveries from GC/MS analysis are poor. They are also difficult to be detected by other methods (e.g., FT-IR) due to their low ambient levels. This study has proven that PTR-MS could the most sensitive, efficient and rapid method to detect ambient OVOCs. |
