- 期刊
淺談於土壤介質中測定環境新興污染物：以抗生素為例
Technical Review of the Challenges of Determining the Emerging Contaminants in a Soil Matrix: Using Antibiotics as an Example
摘要
隨著製藥技術進步及發展，新的污染物也相繼產生，這些在環境中檢測到的抗生素、雌激素及環境荷爾蒙，可能危害生態系統及人體健康。它們隨著工業廢水、家庭污水或廢棄物等不同的途徑進入飲用水水源，已然成為新的環境問題。許多水體中都能檢測出這些新興污染物。目前有大量研究投入調查其於環境中濃度的分布。其中從水體中濃縮萃取新興污染物之技術雖已漸趨成熟，然而土壤的成分複雜，造成這些微量有機污染物難以從土壤樣品中萃取。其萃取回收效率在不同的固體樣品變異很大，且新興污染物於土壤中的萃取方式及濃度測定尚有很多研究與改進的空間。本文以抗生素為例，探討新興污染物在台灣可能產生的問題及於土壤介質中檢測之困難。本文根據財政部關稅署公布的進口的原料藥數量推估台灣抗生素年使用量約為二千公噸，量大不容忽視。這些藥物存在環境中，將危害微生物的生長或增加病原體之抗藥性，干擾生態系統且危及人體健康。然而土壤與抗生素之吸附機制複雜，受土壤本身特性（如黏土礦物成分、ph及有機質）與污染物本身之化學性質（如溶解性、親／疏水性）影響。黏土礦物及有機質為土壤化學性質最活躍的兩個固體成分，對有機污染物均有較強的吸附作用。而有機化合物在土壤上的吸附包括表面吸附（adsorption）和分配（partition）兩種型式。抗生素與土壤之間的作用力複雜，干擾因子亦多，造成檢測的困難。土壤中的抗生素需先克服強大複雜的吸附力量分離到液相中，因此檢測環境中此類化合物程序繁瑣，樣品需要先經過提取（extraction）、淨化（clean-up）後定量（quantification）。而每一程序需依環境樣品的特性及污染物種類則有不同的前處理及檢測分析的選擇。文獻顯示，加壓／加溫萃取（pressured liquid extraction）與以固相萃取（solid phase extraction）淨化樣品為目前最受歡迎之樣品前處理程序，而液相層析結合串聯質譜儀則為最靈敏之檢測方式。然而研究結果顯示目前並沒有一個很有系統且回收率高又穩定的方法通用於抗生素於土壤樣品的萃取。開發從土壤中分離待測污染物的方法尚有許多努力的空間，因此監測新興污染物於土壤中濃度的研究尚缺，更遑論檢測這些污染物在環境中的降解產物與探討降解機制。唯有精確定性／定量污染物，並配合學理上新興污染物可能之降解模式，才能正確評估這些污染物在環境中之流佈，及所可能帶給人類及生態之危害與風險。
並列摘要
Technological advances the pharmaceutical industry are producing many new drugs which benefit our daily life. However, this process also produces new pollutants, including antibiotics, endocrine disruptor compounds, household chemicals and nanomaterials, which pose a threat to the ecosystem and human health. These emerging contaminants may be discharged from industrial waste, domestic sewage and agricultural runoff, thus causing new environmental problems. In this study antibiotics are used as examples to illustrate not only the difficulties of detecting emerging contaminants in soil samples, but also the potential problems they may cause if the amounts cannot be accurately quantified. According to the import and export documentation released by the Taiwan Customs Administration, part of the Ministry of Finance, the estimated amount of antibiotics used in Taiwan is close to 2 million kilograms annually, a figure that is of obvious concern. Antibiotics can undergo redox reactions with metal oxides and minerals in soil. Moreover, the organic matters and mineral constituents of soil can effectively adsorb organic pollutants, such as antibiotics. Although antibiotics cannot be degraded by microbes easily, because of their antibacterial nature, soils provide a good environment for microorganisms to grow within, making biodegradation possible. Soils thus play an important role in the fate of antibiotics in the environment. The quantification of emerging contaminants in the liquid phase has been well established, with contaminant levels reported in range of ng/L to μg/L. However, due to the complexity of soil minerals and organic matters, as well as the structural complexity and instability of organic compounds, detecting antibiotics in soil can be very challenging, and this issue has not been fully studied. The adsorption mechanism between antibiotics and soil is discussed in the current work in order to deduce the best extraction approach. The major sorption mechanisms in soils are surface adsorption and hydrophobic partition, which are affected by the mineral types, pH and organic matter content in the soil. In addition, most antibiotics are comprised of a non-polar core and multiple protonated functional groups. They are thus sensitive to the pH of the medium and adsorb strongly on soils. Such strong and complex forces between soils and antibiotics result in incomplete extraction of antibiotics, causing significant analytical problems. Complete analytical procedures include extraction, clean-up and quantification. It is widely accepted that pressured liquid extraction, followed by solid phase extraction to clean-up the extractant, is a good sample pretreatment process. In terms of quantification, liquid chromatography with tandem mass detector gives better separation and sensitivity than using fluorescence detectors or UV detectors. However, the approaches reported in the literature are only feasible for certain types of compounds in some specific samples. Soil properties, such as organic matter and texture, can affect soil porosity and continuity of the pore space, and thereby affect extraction efficiency, which varies dramatically from case to case. The analytical results are thus not reproducible. The analytical methods for determining emerging contaminants in soil are not well-established, and more efforts should be made to improve the reproducibility, consistency, and efficiency of the extraction process. As people are becoming more concerned about the potential adverse effects of emerging contaminants and their migration in the environment, it is imperative to develop a deeper and broader knowledge about the types of effects, the quantities of the significant contaminant compounds, and the probability of their impacts. More research is thus necessary to provide a solid foundation to understand the transport of organic pollutants in soils, to help reduce their potential toxicity, to provide pollutant control strategies for environmental restoration and protection, and to decrease the risk of polluting the environment. More efforts should be made to investigate the contamination levels of these pollutants in order to properly estimate the risk they may cause. The generation of reliable data greatly depends on the use of an efficient extraction method.