張慧嫺－台灣地區飲用水中含鹵乙酸之分析與流佈調查
Analysis and Distribution of Haloacetic Acids in Drinking Water of Taiwan
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目前全球各地自來水廠大多添加含氯的消毒劑來確保水質安全與衛生。然而，這些消毒劑與水中人為及天然之有機物作用即產生消毒副產物（ Disinfection By-Products， DBPs），其中三鹵甲烷（ Trihalomethanes， THMs）為最主要的消毒副產物物種，約佔20 ％ ；其次即為含鹵乙酸（ Haloacetic Acids， HAAs），約佔消毒副產物的10-13 ％ 。目前含鹵乙酸已經動物實驗證實具有肝毒性、神經毒性、胚胎毒性、生殖毒性、基因毒性等，甚至可能引起最受關切之致突變性或致癌性，因此鹵乙酸在飲用水中之分析與散佈逐漸受到學者重視。
不過目前9種含鹵乙酸物種中，尤以較具健康效應之含溴三鹵乙酸長久以來面臨分析上的困難，不但衍生效率不高，也容易在高溫下裂解為三鹵甲烷，使得飲用水中含鹵乙酸濃度定量不易，且較缺乏大規模的調查數據。 本研究根據美國環保署於1995年所公告之Method 552.2， 針對鹵乙酸的分析進行一系列的改善測試，並加以調查分析目前台灣各地區飲用水中含鹵乙酸的濃度散佈現況。
本研究結果顯示含鹵乙酸前處理之測試最佳條件如下：使用4 ml MTBE做為萃取溶劑，以2ml 10 ％ 硫酸甲醇溶液 ， 75℃，30分鐘之水浴進行衍生後，衍生之乙酸甲酯以4ml 10 ％ 硫酸鈉溶液萃取，最後樣本添加 1ml的正己烷後，再經吹氮濃縮，並注入氣相層析質譜儀（GC-EIMS）以SIM mode設定分析。本研究之9種含鹵乙酸之方法偵測極限介於0.25-1.48μg/L之間。
另外，民國 92年9月至93年5月的採樣分析結果顯示，台灣各地區9種含鹵乙酸總濃度大約分佈在ND-117.44μg/L之間 ，若以現行美國環保署之管制標準評量，大多都符合五種含鹵乙酸總濃度 60 μ g/L以下之標準。然而各地區主要由於飲用水水源水質特性不同及區域性污染性質與行為上的差異，使得各地區含鹵乙酸物種及濃度的分佈上也有所不同，因此，各地區應針對區域性的特殊水質處理相關現況加以改善與控制，來降低飲用水中含鹵乙酸的生成與散佈。
Water treatment plants generally use chlorine as disinfectant to ensure the safety and health of drinking water. However, disinfection by-products (DBPs) may formed by reactions between chlorine and natural organic matter in water. The primary group of DBPs are the trihalomethanes(THMs), which accounts for about 20％of DBPs. The second most prevalent group of DBPs are the haloacetic acids(HAAs), which explains for additional 10-13﹪of DBPs . Over the years, many researchs had prove that HAAs had hepatoxicity, neurotoxicity, embryotoxicity, reproductoxicity and genotoxicity. HAAs even can cause mutation or cancer. For these reasons, more and more researchers pay much attention to the analysis and distribution of HAAs in drinking water.
However, many difficulties were experienced for analysis of bromic trihaloacetic acids by GC-MS. These three HAAs not only had poor efficiency for acidic methanol methylation, but also easily decomposed to form trihalomethane at high temperature. It was difficult to quantify the concentration of HAAs in drinking water. Based on USEPA Method 552.2, this study develops a series of experiments to propose a preferable analytical method for HAAs in drinking water. This study also investigates the distribution of HAAs in Taiwan.
For best analysis of HAAs, some procedures were proposed. In sample preparation, the extraction solution is 4ml methyl tert-butyl ether(MTBE), and the methylation solution is 2ml of 10％sulfuric acid in methanol. The derivatization temperature is 75℃, and derivatization time is 30 minutes in water bath. After methylation, the acidic methanol mixture extract with 4ml 10％ sodium sulfate solution. At last step, 1ml hexane was added to the mixture. After concentration with nitrogen gas, the mixture was then injected to GC-EIMS with selected ion monitoring (SIM) mode. The MDLs for all nine HAAs are between 0.25μg/L and 1.48μg/L.
Furthermore, in the results of the drinking water samples collected between September 2003 and May 2004, total HAAs concentration are between ND and 117.44 μg/L in Taiwan. To compare with the regulation of USEPA, most concentrations of five HAAs are below the maximum contaminant level(MCL) of 60μg/L. However, due to the special water quality of source water and different contamination, there are many differences between species and distribution of HAAs in different area.