- 學位論文
全氟化合物在溼地環境之分布與宿命
Distribution and fate of perfluorinated compounds (PFCs) in wetland environment
摘要
本研究主要探討全氟辛酸(perfluorooctanoic acid, PFOA)及全氟辛烷磺酸(perfluorooctane sulfonate, PFOS)於人工溼地模場中之分佈情形，並評估四種水生植物(大安水蓑衣(Hygrophila pogonocalyx Hayata)、空心菜(Ipomoea aquatic Forssk)、台灣水龍(Ludwigia(x) taiwanensis)及野荸薺(Eleocharis dulcis))對於PFOA及PFOS之攝取能力，以及了解不同溼地土壤在不同條件之下，包括土壤有機碳含量及水中無機鹽類存在，對PFOA及PFOS之吸附能力影響。 四種水生植物皆具有攝取PFOA或PFOS之能力，隨時間增加，攝取量有增加的趨勢，其中以大安水蓑衣對於PFOA及PFOS之攝取能力最佳，其次依序為空心菜 > 台灣水龍 > 野荸薺。且不同植物對PFOS的最終攝取量均較PFOA來的高。模場溼地土壤吸附PFOA及PFOS於6至8日之後可達到平衡濃度，最終平衡濃度為2 ~3 μg/g。而PFOA及PFOS於水中之最終去除率分別為77 ~ 82%及90 ~ 95%，證明人工溼地可有效去除PFOA及PFOS，而其去除之主要機制仍為土壤吸附(sorption onto soil)及植物吸附(phytoextraction)，生物降解、光解及揮發作用等去除機制則可忽略。 比較4種不同溼地土壤及1種標準土壤對於PFOA及PFOS之吸附結果，發現土壤對PFOS的吸附量相較於PFOA為高，代表PFOS對於土壤的親和力較高。而土壤吸附PFOA或PFOS之能力對應土壤分析中有機碳含量(foc)之結果，發現土壤有機碳含量越高對於吸附PFOA及PFOS之能力則有越強的趨勢。吸附平衡狀態下，結果顯示於相同土壤下，PFOS之Kd值皆較PFOA之Kd值為大。土壤S對於PFOA或PFOS相較於其他土壤容易進行吸附，此結果與前述土壤有機碳含量越高對於吸附PFOA及PFOS之能力則有越強之現象相互呼應。 PFOA及PFOS之Kd值隨著三種無機鹽類之離子強度增加而有增加之趨勢，且CaCl2之Kd值> NaCl > Na2SO4。推測原因為在高無機鹽類之離子強度下，電雙層被壓縮造成土壤表面界達電位降低，減少土壤與PFOA及PFOS之間的靜電排斥力，進而相對增加該兩者間疏水性吸附之情形。而PFOA及PFOS之Kd值會隨腐質酸之濃度增加而有降低之趨勢，此現象推測因水中腐質酸表面之官能基與PFOA及PFOS產生錯合之交互作用，降低PFOA及PFOS吸附於土壤表面之機會。 因此不論是土壤中之有機質或水體中之有機質，皆會影響PFOA及PFOS之吸附行為。於土壤中有機質影響方面，土壤有機碳含量越高對於土壤吸附PFOA及PFOS之能力則越強；於水體中有機質影響方面，隨水體中之腐質酸濃度增加時，土壤對於PFOA及PFOS之吸附能力有降低之趨勢。因此由本研究之實驗結果可知有機質(無論土壤本身或水體中)之存在為影響PFOA及PFOS之吸附行為的重要參數。
並列摘要
Removals of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in pilot-scale field and sorption of PFOA and PFOS onto five types of soils were investigated in this study. Phytoextraction by four aquatic plants (Hygrophila pogonocalyx Hayata, Ipomoea aquatic Forssk, Ludwigia (x) taiwanensis and Eleocharis dulcis) and sorption onto soil were determined. Both PFOA and PFOS were fairly phytoextracted by four aquatic plants; the uptake capacity was found in the following order: Hygrophila pogonocalyx Hayata > Ipomoea aquatic Forssk ≈ Ludwigia (x) taiwanensis > Eleocharis dulcis. In the soil sorption experiment, equilibrium for PFOA and PFOS were achieved within 6 to 8 days; sorption capacity of 2–3 μg/g was observed at the end of the 15-d experiment. Experimental results and literature review suggest that phytoextraction and soil sorption were the most significant mechanisms for PFOA and PFOS disappearance in the pilot-scale constructed wetland, while contributions of biodegradation, photolysis, volatilization and hydrolysis were negligible. Effects of inorganic salts (CaCl2, NaCl, and Na2SO4) and humic acid in solution on the extent of sorption of PFOA and PFOS were also evaluated. The results indicated that all types of soils had a higher affinity for PFOS than for PFOA. The extent of sorption for PFOA and PFOS increased with fraction of organic carbon (foc) of soils. The partition coefficient (Kd) values of PFOA and PFOS increased with foc and ionic strengths of inorganic salts. On the contrary, the Kd values decreased with an increase in the concentrations of humic acid in the solution. The existence of organic matters is the parameter dominating the sorption behaviors of both PFOA and PFOS onto all types of soils studies. In addition, the presence of inorganic salts also affects PFC’s sorption behaviors.
參考文獻
延伸閱讀
- 簡銘延（2015）。全氟碳化物於大鼠中分配係數之研究〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2015.02110
- 陳炯博（2010）。多功能性氟共聚物之合成與應用〔碩士論文，崑山科技大學〕。華藝線上圖書館。https://doi.org/10.6828/KSU.2010.00042
- 吳瑞鑫（2010）。溼氣交聯型含氟或矽烷PU樹脂在織物撥水功能的應用〔碩士論文，淡江大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0002-2007201001594500
- 黃智鋒（2005）。Aquatic Plants Influence Treatment Performance in Constructed Wetlands〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2005.01297
- Ciou, P. S. (2009). Stability of Perfluorinated Compounds and Thier Occurrence at the Industrial Wastewater Treatment Plant and Downstream Rivers [master's thesis, National Taiwan University]. Airiti Library. https://doi.org/10.6342/NTU.2009.02182