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標題: | 飽和脂肪烴於臺灣西南海域事件沈積層中分布與特徵之研究 Distribution and characteristics of Aliphatic Hydrocarbons within the natural geohazard event-layer in southwestern Taiwan |
作者: | Che-Yuan Chi 紀喆元 |
指導教授: | 蘇志杰(Chih-Chieh Su) |
關鍵字: | 高屏海底峽谷,枋寮海底峽谷,屏東地震,莫拉克颱風,正烷類, Gaoping Submarine Canyon,Fangliao Submarine Canyon,Pingtung Earthquake,Morakot Typhoon,n-alkanes, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 臺灣西南海域每年接收來自臺灣南部島嶼型河川四千九百萬噸陸源沈積物,加上具有狹窄陸棚及多條海底峽谷,被認為是研究陸源物質源到匯的最佳場所。2006年屏東地震及2009年莫拉克颱風所觸發之海底濁流或異重流,將大量沈積物傳輸至深海,進而促使深海事件沈積層的碳埋藏較非事件時期高出近兩個數量級,顯示海底地質災害所致之快速堆積對於陸源有機碳埋藏十分重要。本研究挑選2006~2013年期間海研一號和海研五號採集的11根岩心,範圍包括高屏海底峽谷、枋寮海底峽谷及高屏陸坡,以生物指標中最為廣泛且常見的正烷類作為探討依據。由於正烷類能提供生產者的資訊用以推敲其來源,且因其耐降解而不易消失的特性,因此被廣泛的應用。分析結果顯示,枋寮海底峽谷上段、陸坡盆地及高屏海底峽谷下游岩心具有明顯的海源正烷類(碳數小於25的正烷類)偶數碳訊號(0.11~1.34 μg /g),主要為正十八烷(Octadecane, C18)及正二十烷(Icosane, C20),而陸源長正烷類(碳數大於等於25的正烷類)訊號相對低(n.d.~0.58 μg/g)。除陸源訊號強度低之外,再加上高屏溪本身傳輸入海之CPI趨近於1特性,使得大部分岩心正烷類指標研究結果相近,CPI值變化介於0.74 ~ 2.07之間,唯獨包含植物碎屑的沈積層CPI值才大於5。岩心正烷類指標值分析結果顯示,當極端事件與高屏溪輸出有關時,呈現與一般沈積層相似的迴歸線。但當事件堆積與河流輸出無關(如屏東地震事件)時,則具有斜率明顯不同的趨勢分布,顯示正烷類指標趨勢與誘發沈積物傳輸的機制有關。基本上遵循離海底峽谷越近,陸源訊號越強的趨勢,而且顯示沈積物循峽谷傳輸並往深海匯集,此一結果與之前海底電纜斷纜事件的相關調查相呼應。總結所觀察到的結果,各岩心碳鏈訊號在事件和非事件層之間特徵變化並不太明顯,但利用多根岩心綜合討論仍可以分辨出特定事件層。而正烷類分析結果,提供了沈積物因極端事件循峽谷傳輸的有利證據。 Every year, 49 million tons of the suspended sediment transport from small mountainous rivers to the southwestern Taiwan shelf and slope and, the Gaoping Submarine Canyon (GSC) and the Fangliao submarine canyon (FSC) cuts across the Slope and Shelf. Therefore, Taiwan has become a perfect source to sink research area. After the 2006 Pingtung Earthquake and 2009 Morakot Typhoon which triggered gravity flows and, transported huge amount of sediments and substantial organic carbon into deep sea. According to previous study results of δ13C, Total organic carbon, and the 210Pb-derived sediment accumulation rates, this study attempts to use n-alkanes as the biomarker for investigating organic matter transportation. The n-alkanes can be used to trace the source which it had been manufactured. Owing to the n-alkanes is stable, it is widely used as an important geochemical tracer. We followed the previous study which distinguished events and non-event layers. The cores which collected from GSC, Gaoping Slope and FSC are used for n-alkanes distribution and characteristics analysis. The analysis results show the terrigenous n-alkanes concentration is ~0.58 μg/g, and plenty of Octadecane and Icosane were found in sediment samples. The distribution of n-alkanes indicates most of the organic matter in sediments are from algae. The carbon preference index (CPI) of riverine sediments, shows the values are close to 1. The regression of n-alkanes and CPI reveals two trends in the regression line. One is related to the transportation of the organic matter from GSC. Another trend is related to the 2006 Pingtung Earthquake triggered debris flow. In conclusion, the n-alkanes as the biomarker is a good geochemical tracer, but it is not easy to be used in modern sediments offshore SW Taiwan. However, this biomarker still discriminates two different sources and transportation paths of sediments transported in the submarine canyons, and the evidence of the sediments transported by extreme natural geohazard events. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/74978 |
DOI: | 10.6342/NTU201904086 |
全文授權: | 有償授權 |
顯示於系所單位: | 海洋研究所 |
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