| 摘要: | 二仁溪為台灣南部污染較嚴重的河川，底泥中更是累積了釵h的污染物，本研究以生物淋溶的方法，去探討二仁溪底泥中重金屬溶出的可能性、淋溶過程中底泥物化因子的變化，以及是否有伴隨多環芳香碳氫化合物(PAHs)的釋出。生物淋溶的過程一般需藉由底泥中的原生硫氧化菌作為淋溶時所需之微生物，本研究係在不同操作條件下(原始底泥有滅菌下並添加基質與不添加基質、原始底泥無特別滅菌下不添加基質與添加基質)探討淋溶過程中底泥之物化因子的變化。並且利用逐步萃取法(Sequential Extraction Procedure, SEP)來分析底泥中重金屬各鍵結型態組成(包括可交換態，與碳酸鹽鍵結態，與錳氧化物鍵結態，與鐵氧化物鍵結態，與有機物鍵結態及殘餘態)於生物淋溶過程中的變化。
研究結果顯示，底泥在無滅菌並添加基質之生物淋溶試程對於金屬的溶出效果較佳，能在最短時間內達到最終pH值(2.20)。同時，淋溶過程中硫氧化菌氧化基質硫產生硫酸鹽的同時，釋出氫離子，使pH值逐漸下降，氧化還原電位則隨pH值的下降而上升。在其它試程中，也發現可藉由生物反應與化學反應來產生氫離子。
淋溶過程中，底泥顆粒質地分佈在坋粒範圍之重量百分比逐漸增加，同時也因粒徑逐漸變小，造成比表面積的逐漸增大。由SEM/EDX分析發現，微量元素中的元素氧有明顯增加的趨向。而於金屬之淋溶效果最佳之無滅菌但有添加基質之試程中，PAHs則隨著pH值下降而有明顯釋出的現象。由四種不同條件之淋溶試程發現，淋溶過程中各種金屬之鍵結型態大致相同，而在十種金屬中只有鎘跟鈷鍵結型態相似，主要是以與碳酸鹽鍵結態和與有機物鍵結態為主；鉻跟鐵相似，主要是以與鐵氧化物鍵結態和與有機物鍵結態為主；錳和鉛相似，主要是以與鐵氧化物鍵結態、與有機物鍵結態和與碳酸鹽鍵結為主。
比較生物淋溶前後重金屬溶出效率之結果則發現，無特別滅菌但有添加基質的條件下溶出效果最好，十種重金屬之溶出率高低依次為：鎳(63.50﹪)＞鐵(59.83﹪)、銅(59.01﹪)、鋅(57.60﹪)＞鉻(47.05﹪)＞鉛(39.23﹪)、錳(38.69﹪)、鈣(38.40﹪)＞鎘(25.37﹪)、鈷(18.02﹪)；其他試程中，由於底泥需滅菌或沒有添加基質，使淋溶過程所需長久時間才能達到最終pH值，或因短時間就達到穩定之最終pH值，於過程中並無釋出很多的氫離子來使pH值下降，造成金屬溶出效果並沒有如同底泥在無特別滅菌但有添加基質的試程時佳。
The aim of this study is to find the possibility of metal released from sediment, the variation of physicochemical factors in sediment and the accompanying release of PAHS by bioleaching. The experiments were designed under four different operational conditions which varied in sediment sterilization and substrate adding each other, to find the variation of physicochemical factors and binding fractions in sediment.
Results reveal that the most significant leaching effect of metals from sediment could be found in the test operated under the condition with sediment non- sterilization and substrate adding. Meanwhile, the pH of sediment decreased with time whereas the ORP increased.
Particle size distribution tended to concentrate on the range of silt in the process of bioleaching. Meanwhile, the specific surface area of particles increased with the decrease of particle size as well as element oxygen in particles increased. The releases of 4-rings, 5-rings and 6-rings PAHS in the test operated under the condition with sediment non- sterilization and substrate adding significantly increased with the decrease of sediment pH.
Among the process of bioleaching, it can be noted that the variation of binding fractions of different metals was insignificant. Cadmium similar to cobalt, mainly bound to carbonates and organics; chromium similar to iron, mainly bound to Fe-oxides and organics; manganese similar to lead, mainly bound to Fe-oxides, organics and carbonates.
The order of metals released from sediment found in the test operated under the condition with sediment non- sterilization and substrate adding was as follows: Ni(63.50%), Fe(59.83%), Cu(59.01%), Zn(57.60%), Cr(47.05%), Pb(39.23%), Mn(38.69%), Ca(38.04%), Cd(25.37%), Co(18.02%). |
