多接收器感應耦合電漿質譜儀(MC-ICPMS)之鉬同位素分析技術及貝加爾湖岩芯中鉬同位素之研究

Analytical techniques for molybdenum isotopes by using Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) and its application to a sediment core from Lake Baikal

劉信廷

指導教授 ： 余英芬 ； 李德春

國立臺灣師範大學/理學院/地球科學系/碩士(2013年)

摘要

鉬元素的研究主要集中於海洋環境上，而湖泊中鉬元素的研究則相當缺乏，因此本研究使用貝加爾湖岩芯標本來進行探討。本論文係用序列萃取方式萃取沉積物中鐵錳氧化物所吸收之微量元素，並透過本研究工作所建立之層析方法純化並分離鉬元素。最後利用雙示蹤劑(由97Mo與94Mo配成)解析法(Double spike method)於多接收器感應耦合電漿質譜儀(MC-ICPMS)進行鉬同位素分析。
在貝加爾湖中，鉬同位素的變動是受控於何種機制影響，是本篇研究欲應用及探討之目標。由於利用鐵錳相萃取的方式可推算出水體可能代表的同位素訊號值，故貝加爾湖岩芯沉積物經鐵錳相萃取後,再經層析純化及雙示蹤劑同位素分析技術量測得到的鉬同位素值，即為貝加爾湖湖水水體鉬同位素值之回推。此淡水湖泊水體的鉬同位素值回推為98/95MoNIST3134= 1.02‰。此外，貝加爾湖岩芯的記錄顯示，以岩芯深度100公分(即年代12ka)為界，可反映該湖水體於上次冰期及間冰期以來前後兩不同階段的氣候變動趨勢。由多種證據推論，貝加爾湖湖水鉬同位素值的變動應是受冰期與間冰期氣候變遷下其是否受冰川覆蓋的影響導致不同程度的氧化結果所致為較可能的機制。

關鍵字

雙示蹤劑解析法 ； 貝加爾湖岩芯 ； 上次冰期與間冰期湖泊的鉬同位素值變動

並列摘要

The studies of molybdenum (Mo) are mainly focusing on marine environment, and the application on lake record is rare. A three-meters long gravity core (GC-99; 52°05’23”N, 105°50’24”E; water depth 201m) from Lake Baikal is studied for Mo isotopes. This study is using Mo concentration and its isotope fractionation to examine the sources of material and the changes in conditions of Lake Baikal with climate changes.
To approach on extracting Mo isotope signal directly related to lake water, a sequential leaching technique to extract the Mo isotopes coating on the Fe-Mn oxides is established, and a robust chromatography technique to purify molybdenum isotopes is modified from previous study. Then, Mo isotope composition is measured by applying double spike method with Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS). According to the Mo concentration and its isotope composition, the results imply Lake Baikal stayed oxic condition over the last 24 ka. Moreover, the sediment core GC-99 from Lake Baikal imply two stages fluctuations of the lake environment separated at core depth of 100cm (around 12ka); and the shifting of 98/95Mo isotope composition shows that the lake during interglacial period was more oxic than the last glacial period due to absence of ice cover.

並列關鍵字

Double spike method ； Lake Baikal ； The changes in molybdenum isotope compositions over the glacial to interglacial

參考文獻

陳志華 (2010) 南海沉積物自生鐵錳氧化物中稀土元素及釹、鉿同位素成分：重建南海過去三千萬年以來深水循環之演化史。國立成功大學地球科學研究所碩士論文。

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