台灣北部火山地區鐵、鋁和其他重金屬的晝夜循環

Diel Cycle of Iron, Aluminum and Other Heavy Metals in a Volcano Watershed in Northern Taiwan

高書暘(Shu-Yang Kao)

指導教授 ： 呂學諭

國立中正大學/理學院/地球與環境科學系應用地球物理與環境科學研究所/碩士(2014年)

摘要

本研究選擇台灣北部大火山群中的酸性水體北磺溪作為研究標的，觀察金屬元素在水中的濃度晝夜變化現象。對兩個採樣點同時進行24小時的連續採樣，分別為上游的八煙(pH=4.03)和下游的三合橋(pH=4.24)，進行時間與空間序列的分析。
在本次實驗中，除了鐵、砷和釩有明顯的晝夜變化趨勢之外，其他元素包含主要元素、稀土元素皆無明顯的晝夜變化趨勢。由於受到pH值在晚上增加的緣故，鐵的濃度在白天增加，晚上時形成三價鐵沉澱移除而降低水中濃度。砷和鐵有完全相反的趨勢，在這個pH值區間砷以帶負電的陰離子團形式存在於水體，白天鐵在水中的濃度較高，砷會吸附於水中的氧化鐵水合物，造成白天時砷的濃度降低，夜晚時砷則會重新脫附於水體，造成砷濃度的增加而表現出晝夜變化的趨勢。釩在水中的特性與砷相反，以帶正電的陽離子存在於水體，故帶正電的釩晝夜變化趨勢與帶負電的砷完全相反，砷與釩都是藉由對氧化鐵水合物的吸脫附作用來改變水中的濃度，因此這兩種在水中帶相反電性元素呈現出的晝夜變化趨勢也完全相反。

關鍵字

火山地區 ； 晝夜循環 ； 重金屬 ； 砷

並列摘要

Diel changes in concentration of trace elements were investigated in North Huanghsi River, which is located at Tatun Volcanic Group and drains the volcanic geothermal spring water northward to the coastal area. A 24-h sampling procedure was conducted at two sites: BY (the upstream site) and SH (the downstream site).
According to the results of chemical analysis, only Fe, As and V show considerable diel concentration cycle while the others including rare earth elements demonstrate insignificant diel change. Along with the increase of pH value at night, the concentration of Fe decreases due to the transformation from Fe2+ (higher solubility) to Fe3+ (much lower solubility). Therefore, iron hydroxide would be significantly generated at night and would probably dominate the adsorption behavior of ions. In general, iron hydroxide is in the form of positive charged ion under the low pH environment. On the contrary, As is an anionic complex. It is expected that As can be adsorbed and consequently precipitated with iron hydroxide in the form of negative charged ion. Therefore, a lower concentration of As was observed in the late afternoon in this study. In addition, it is interesting that V demonstrates an opposite behavior with As during the diel cycle. This implies that V is in the form of positive charged ionic complex under the low pH environment and shows a quite different cycle from As.

並列關鍵字

Volcano ； Arsenic ； Diel

參考文獻

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