| 摘要註: |
研究主要分為三部分，分(1)溼地實驗，(2)盆栽實驗，(3)吸附實驗。在溼地實驗瞭解水體重金屬於溼地系統中主要以吸附土壤為主要去除機制，銅鋅於控制組內去除率為79.7及82.8%，於香蒲組去除率則為82.8及91.8%，於蘆葦組去除率則為82.8及91.5%。三溼地系統之土壤以分段萃取分析結果顯示，土壤與重金屬銅鋅主要以有機鍵結、碳酸鹽鍵結及硫化物鍵結存在。香蒲吸收重金屬銅鋅累積量分別為36.4、97.7 mg/kg，蘆葦銅鋅累積量則為28.4、84.8 mg/kg，植體吸收重金屬主要以根部為主要累積處。在香蒲蘆葦系統BCF均大於1，表示植體根部可吸收較土壤更多的重金屬，而TF值均小於1其表示植體根部累積較莖葉更多的重金屬。 而盆栽實驗中螯合劑萃取重金屬銅鋅結果以DTPA效果最佳，其次為EDTA、EDDS，檸檬酸則係最差。土壤由有機質含量區分為高有機質土壤及低有機質土壤，其中低有機質土壤弱鍵結比例較高有機質土壤多。而添加螯合劑改變土壤與重金屬銅鋅鍵結型態以DTPA提升弱鍵結比例最佳，其次依序為EDTA、EDDS及檸檬酸。盆栽實驗中以向日葵吸收重金屬效益最佳，其次為油菜，而香蒲及蘆葦則係最差。添加螯合劑可改善植體根部重金屬吸收，以添加DTPA效果最佳，其次依序為EDTA、EDDS，添加檸檬酸則僅有些許之提升。而螯合劑添加對於植體重金屬傳輸亦有提升，其中以添加EDDS對於植物重金屬傳輸效益最為顯著，其原因為EDDS與重金屬之錯合物可穿透植體根部卡氏帶，故能提高植體對於重金屬之傳輸。 吸附實驗中四種植體向日葵、油菜、蘆葦及香蒲表面皆帶負電，故對於重金屬吸附具有可行性。而植體吸附以Langmuir為最佳等溫吸附方程式，植體對於銅吸附量以油菜為最，其次分別為向日葵、蘆葦及香蒲，銅吸附量分別為1731、1451、179及160 mg/kg;植體對於重金屬鋅亦以油菜吸附量最高，其次為向日葵、蘆葦及香蒲，吸附量則分別為884、703、144及117 mg/kg。本研究結果顯示添加螯合劑對於植物萃取具提昇之效益，且收割回收後之植體可作為生物吸附劑之材料。 This study included metal redaction investigation within wetland stsyems, phetoextration to remove soil metal contamination via pot tests, and recovered macrophytes metal adsorption experiments. Three pilot-scale consrructed wetlands were employed to investigate heavy metal removal receiving river water contaminated by confined swine operations. Significant total recoverable copper and zinc reduction were 80 and 91% for control, 83 and 92% for cattail, and 83 and 92% for reed wetland systems. Based on sequential extraction results, copper and zinc in wetland sediments of wetland systems were mainly organically, carbonate bound, and sulfide bound. For two vegetation systems, both Cu and Zn concentrations in above and belowground biomass were in the order of root>stem>leave. In vegetated systems, metals were accumulated in roots greater than the concentration in adjacent sediments with BCF of ≧ 1. Metals in leaves and stems were lower than half that of roots. Phytoremediation is a green remediation technology for cleann-up contaminated soils. The effect of chelant addition including EDTA, DTPA, EDDS, and citric acid on phtoextraction of metals into macrophytes was investigated in this pot test. The extraction efficiency results was observed as the following ranking, DTPA > EDTA > EDDS > citric for Cu and Zn. The higher extraction capability can be predicted by stability constant of Cu-chelant complexes (logK(Cu-DTPA2-) = 21.2; (logK(Cu-EDTA2-) = 20.5; (logK(Cu-EDDS2-) = 18.4; (logK(Cu-citric acid2-) = 7.6). While the stability constant of Zn-chelant complexes were (logK(Zn-DTPA2-) = 18.3; (logK(Zn-EDTA2-) = 16.5; (logK(Zn-EDDS2-) = 13.5; (logK(Zn-citric acid2-) = 6.06). DTPA, EDTA, EDDS and citric acid enhanced Cu and Zn uptake efficiency. EDDS was the most effective chelants compared to other chelants in stimulating the translocation of metals from roots to shoots. The primary mechanism was induced by metal chelant complexes entering the root through breaking in the endodermis of the root and the Casparian strip, therefor metal chelant can be rapidly transported to the above ground parts of macrophytes. The adsorption mechanism of metal removal by four commonly used phytoremediation macrophytes biomass including sunflower, Chinese cabbage, cattail, and reed was investigated. The metal adsorption data were fitted with the Langmuir and Freundlich isotherms and presented the Langmuir is the best fitted model for all biomass tested. The maximum sorption capacity Qmas of Cu was 1482, 2000, 200, and 238 mg/kg while the Qmas of Zn was 769, 1111, 133, and 161 mg/kg for biomass sunflower, Chinese cabbage, cattail, and reed, respectively, predicated by the Langmuir model. The biomass of sunflower, Chinese cabbage, cattail, and reed all possess the potential to be employed as biosorbents to remove Cu and Zn from aqueous solutions. |