快速質譜技術應用於空氣中有機汙染物監測

李郁掄(Yu-Lun Li)

指導教授 ： 王家麟

國立中央大學/理學院/化學系/碩士(2015年)

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，建立移動實驗室監測方法，並應用於工業區空汙問題診斷，強化現有空氣品質測站、光化測站對於毒性或異臭味化學物質偵測能力的不足。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)應用於工業區排放之揮發性有機化合物(volatile organic compounds, VOCs)鑑定。
本研究將盒鬚圖(Box-Whisker plot, box plot)與雪球式資料抽樣法(snowball sampling)應用於環境污染物資料快速篩檢，能快速從大量觀測資料找出關鍵成分，再透過TOF/MS的高質量解析力(m/Δ= 5000)與資料庫搜尋找出關鍵成分代表之化學物質，建立屬於特定污染場址之化學物質清單，再根據理論計算之半定量濃度逐時變化搭配氣象資料解釋污染物事件成因。
透過建立工業區的排放特性清單，可知「新竹遠東化纖總廠」、「平鎮工業區」、「六輕工業區」的環境重點VOCs以含氧揮發性有機化合物(oxygenated volatile organic compound, OVOCs)為主，「平鎮工業區」的觸發研究以PTR-QMS執行多成分觸發採樣，將高值事件當下觸發採樣保存之樣本攜回實驗室以GC/MS/FID (gas chromatography/mass spectrometry/flame ionization detector)分析108種VOCs。研究結果顯示OVOCs 在綜合性的工業區環境中佔了多數的權重比，占總量16% - 75% (新竹15% - 60%、中壢32% - 84%)，這些OVOCs 很有可能是異味產生的主要元兇，部分會對光化產生之二次臭氧生成造成顯著貢獻。
但除了OVOCs外，含氮有機揮發性有機化合物(nitrogenated volatile organic compounds, NVOCs)也是工業區中不可忽視的汙染物，在「新竹遠東化纖總廠」和「平鎮工業區」的案例中，發現屬於NVOCs之二甲基甲醯胺(N,N-Dimethylforamide, DMF)、嗎啉(morpholine)有明顯的排放情形。
再者，本研究利用PTR-MS數據綿密且時間解析度高的優勢，搭配風場資料解釋汙染物傳輸行為，在「新竹遠東化纖總廠」的個案中，當大量的有機溶劑排放至大氣中，只要大氣擴散條件不良，便容易累積濃度，進而釀成空汙事件，使得周邊居民陳情事件的發生；沿海區域的「六輕工業區」和「高雄都會區」，氣象場受季節性的海陸風氣候影響，細微的氣象場轉變會使得同一處的污染物變化可從數個ppb 或無排放情況，轉為數百ppb 至數 ppm 間的極大差異。

關鍵字

快速質譜 ； 有機汙染物

並列摘要

This study is to develop a mobile laboratory and a diagnostic methodology involving the use of proton-transfer reaction mass spectrometry (PTR-MS) to investigate chemical pollutants released from industrial parks. The establishment is expected to remedy the lack of detecting capabilities of toxic or odorous compounds in existing EPA air-quality and photochemical monitoring stations (PAMS). This study used two types of PTR-MS, quadrupole mass spectrometry (dubbed PTR-QMS) and time-of-flight mass spectrometry (dubbed PTR-TOF/MS) to analyze ambient volatile organic compounds (VOCs) released from industrial parks.
In cope with the large datasets accumulating overtime, box-whisker plotting and snowball data sampling methods were adopted for rapid data screening to facilitate rapid identification of key compounds. With the use of the high mass resolving power (m/Δ= 5000) of PTR-TOF/MS and the chemical database, key VOCs unique to specific pollution sources can be accurately identified. Furthermore, the combined use of concentration variability and field wind data helped interpret the source-and-receptor relationship of pollution events.
Field measurements targeting emissions from Hsinchu Far-East Chemical Fiber Plant, Pingjhen Industrial Park and Mailiao Industrial Park revealed that the majority of the measured VOCs were oxygenated (OVOCs). In the Pingjhen measurement, the trigger-sampling technique was coupled with PTR-QMS to capture plume events from the factory cluster. The triggered samples were analyzed for 108 VOCs by in-lab GC/MS/FID (gas chromatography/mass spectrometry/flame ionization detector) to characterize the chemical composition of the pollution plumes. The results showed that OVOCs accounted for 16% -75% of the total amount of 108 VOCs in Pingjhen (compared to 15% - 60% in Hsinchu and 32% - 84% in Chungli). Such large fractions of OVOCs in the air may explain the frequent odor complaints reported in the vicinity of the industrial parks. Moreover, large emissions of OVOCs may contribute to the production of photochemical ozone.
In addition to OVOCs, nitrogen containing VOCs (NVOCs) were also found in the cases of Hsinchu Far East Chemical Fiber Plant and Pingjhen Industrial Park. Dimethylformamide (DMF) and morpholine were the two prominent NVOCs that are suspected to strongly link with foul odors plaguing neighboring communities.
By exploiting the high data resolution of PTR-MS measurements, concentration spikes were often link to the meteorological conditions. For instance, in the case of the Hsinchu Far Eastern Chemical Fiber Plant, abrupt rise in concentrations were found to associate with poor atmospheric dispersion conditions as well as the change in wind speed/direction. In the coastal areas, such as Mailiao Industrial Park and Kaohsiung (city), the concentrations were significantly affected by the seasonal sea-land breeze, the subtle change of wind made selected VOCs varied from below sub-ppb to hundreds of ppb or even ppm levels.

參考文獻

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