| 摘要: | 有害空氣污染物 (Hazardous Air Pollutants, HAPs) 隨著工業發展被大量排放，其中包括若干具毒性之揮發性有機化合物 (Toxic VOCs)。為求取空氣中 Toxic VOCs 平均濃度以評估長時間暴露下之健康風險，美國環保署已公告一標準方法 U.S. EPA Method 325A/B，利用化學吸附劑以氣體擴散原理吸附空氣中 VOCs，再利用不同吸附材料對於不同化合物之吸取速率 (Uptake Rate) 求出在採樣時期間各目標物的平均濃度。在樣品分析上採用自動化熱脫附儀 (Automated Thermal Desorption, ATD) 搭配氣相層析質譜儀 (Gas Chromatography- Mass Spectrometer, GC-MS) 作為分析系統以更簡易的採樣方法長時間監測周界 HAPs 濃度。
首先，本研究之目的是擬將可分析的HAPs物質數目增加，故合併數種不同化學吸附材料之優勢複合成單一採樣管，以達到廣泛應用之目的。研究重點之一是進行複合式材料之條件優化、測試及採樣的應用，其中包含檢量線之相關係數 (R2)、方法偵測極限 (MDL)、精密度 (Accuracy)、準確度 (Precision) 之儲存穩定性(Storage stability)，以達到嚴格的品保品管 (Quality Assurance/Quality Control, QA/QC) 要求，排除未通過 QA/QC 的物種。研究重點之二是利用自製暴露腔在不同溫度、濕度條件下求取個別目標物之專屬吸取速率用於計算周界HAPs濃度。
本研究考量吸附材料的選擇性，在最佳的複合方式下，結果顯示共可針對69項 HAPs 進行被動式採樣，比起單一吸附材料 Carbopack X 與 Carboxen 569 僅可針對50項及37項 HAPs 高出近30項目標物種。複合式材料檢量線相關係數介於0.990~1.000，方法偵測極限濃度介於0.04 ppbv~0.99 ppbv，精密度相對標準偏差介於0.32%~10.43%，準確度之樣品保存回收率介於74.28%~121.61%，而被動式採樣後之採樣管樣品須保存於4℃環境中，並於14天內分析完畢，以確保樣品品質。
在實驗室內進行實驗評估完成後，分別於各化學實驗室(有機、分析、生化實驗室)、台北中研院、桃園觀音工業區及大園工業區、彰化和美國中及埔心高中、雲林崙背國中、高雄仁大工業區等地進行實場採樣。以上採樣方式包含主動式採樣及被動式採樣，而於本研究當中，利用採樣管採樣有以下四種應用，第一：進行被動式採樣用於長時間的環境評估；第二：被動式採樣與線上熱脫附氣相層析質譜法 (Online TD-GC-MS) 或線上熱脫附氣相層析火焰離子偵測器 (Online TD-GC-FID) 進行比較；第三：利用被動式採樣以佈點的方式追朔排放源；第四：平行比對驗證，將被動式採樣與上述之線上GC分析方法置於同一地點平行採樣分析以驗證彼此可靠性。實場測試結果顯示被動式採樣與 online TD-GC-MS 分析方法的平均值接近，獲得極佳之驗證效果。日後監測目的是為了獲取各 Toxic VOCs 的平均濃度，而非瞬間濃度變化，則可以利用實施簡易之被動式採樣法評估相對較長時間之目標物的平均濃度，擴大對於這類有害物質的環境調查能力。;Hazardous Air Pollutants (HAPs) are emitted in large quantities with industrial development, and the threat to public health has been an issue of great concern in recent years. In the past, the passive sampling technique, similar to the U.S. EPA Method 325A/B, was developed, including the determination of uptake rates for different adsorbent materials for a variety of volatile organic compounds (VOCs) under different climatic conditions.
Firstly, to broaden the range of target compounds, dual commercial adsorbent materials were combined into a tandom adsorbent tube for the complementary benefits and easier deployement and logistics. After excluding the species not passing the QA/QC criteria, the specific experimental uptake rates of the remaining target species were experimentally obtained for calculating concentrations of target compounds after passive sampling. Therefore, another important aspect of this study is to determine the uptake rates with a self-designed exposure chamber under different temperature and humidity conditions. An Automated Thermal Desorption (ATD) with Gas Chromatography-Mass Spectrometer (GC-MS) was used to analze the sorption tubes of passive sampling collected from the field.
The results showed that the composite materials could be used for passive sampling of 69 HAPs, nearly 30 more than the single adsorbent material, e.g., Carbopack X and Carboxen 569, which can only target 50 and 37 HAPs, respectively. The correlation coefficients of the composite materials were between 0.990~1.000, the detection limits were between 0.04 ppbv~0.99 ppbv, the relative standard deviations representing precision were between 0.32%~17.57%, and the recoveries representing accuracy were between 74.28%~121.61%. The samples were stored at 4°C and analyzed within 14 days to ensure the sample and thus data quality.
After thorough preparation, the composite materials were tested in various environments, such as nearby laboratories (organic, analytical, and biochemical laboratories), Academia Sinica, Taoyuan Guanyin Industrial Park. Tayuan Industrial Park, Changhua, and U.S. High School, Puxin High School, Yunlin Lunbei National High School, and Kaohsiung Renda Industrial Park. At some of these sites, both active sampling and passive sampling methods were used. In this study, there are four applications of passive sampling. Firstly, for long-term environmental exposure assessment; secondly, passive sampling with online thermal desorption (TD)-GC-MS or TD-GC with flame ionization detection (FID); thirdly, for emission source investigation; and fourthly, mutual validation with the online TD-GC-MS measurements. Comparing with the online GC method, passive sampling can avoid the complications in operation and maintenance of an instrument in the field. The field tests also revealed comparable results between the two methods when the mean concentrations were compared. As a result, passive sampling can effectively evaluate average concentrations of the target species over a prolonged period at minimal cost and effort, thus adding another useful tool to enhance environmental monitoring capability. |
