高山湖泊底泥沉積物之脂肪族碳氫化合物化學分析

Analysis of Aliphatic Hydrocarbon Compositions In Lake Sediment From a High Mountain Lake

鄭承恩(Cheng-En Cheng)

指導教授 ： 范誠偉

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(2012年)

摘要

本研究主要分析台灣高山湖泊翠峰湖底泥沉積物中脂肪族碳氫化合物(Aliphatic hydrocarbon compositions, AHCs) C10至C35直鏈烷濃度，樣品年代涵蓋860年前至今，以生物指標(Biomarker molecule proxies)評估沉積物中有機物質來源及相對貢獻量。底泥沉積物前處理包括索氏萃取，銅粒除硫及管柱淨化等，以GC-FID進行化學分析。總直鏈烷濃度平均為32.45 ± 6.21μg/g，直鏈烷優勢種順序為C29、C31、C33、C27、C35，佔總AHCs濃度約70％；其中，直鏈烷短碳鏈(C15+C17+C19)、中碳鏈(C21+C23+C25)、長碳鏈(C27+C29+C31)之相對比例分別為3.4 ± 2.2％、14.1 ± 2.3％及82.4 ± 3.5 ％，顯示翠峰湖直鏈烷組成以陸生植物貢獻之長碳鏈直鏈烷為主。翠峰湖沉積物中直鏈烷之CPI（碳優指數）為4.78±1.05，具生物來源訊號；TAR (Terrigenous to Aquatic Ratio)值為35.4 ± 22.4，指出陸生植物相對藻類貢獻明顯；Paq (The aquatic plant n-alkane proxy)值為0.17 ± 0.03，無明顯水生維管束植物來源訊號。而草本相對木本植物直鏈烷比值C31/(C27+C29)為0.45 ± 0.05，顯示生長於集水區之陸生植物，以木本植物為主，並推測860年以來，翠峰湖周遭環陸生植物環境相對穩定。在底泥沉積物21及31公分深處，其較高之直鏈烷濃度(57μg/g及45μg/g)及較低的CPI值(1.71及2.54)，顯示當時除主要來自陸生植物來源之直鏈烷外(TAR, 61.4及48.0)，可能發生侵蝕事件，造成大量較成熟之有機物質進入湖泊，稀釋了直鏈烷中陸生植物訊號，造成直鏈烷濃度增加及較低的CPI值。此外，於13及19公分深處，存在相對較高之短碳數直鏈烷濃度(2.81μg/g及2.05μg/g)及較低的TAR值(分別為6.6及9.1)，顯示當時直鏈烷來自水生環境之藻類貢獻量相對增加，可能代表水生環境之改變，推測當時湖泊水位較高較適藻類生長。

關鍵字

底泥沉積物 ； 脂肪族碳氫化合物 ； 高山湖泊

並列摘要

Aliphatic hydrocarbon compositions (AHCs, C10-C35 n-alkanes ) from a 55-cm sediment core (age ca. 860 yr) of Emerald Peak Lake, the largest high mountain lake in Taiwan, were investigated. The concentrations of AHCs, Soxhlet extracted and GC-FID analyzed, and the calculated biomarker molecule proxies (CPI, TAR, C31/(C27+C29) and Paq,) were used to estimate the organic matter origins and their relative contribution in sediments. The total AHCs concentrations in sediment from Emerald Peak averaged 32.45±6.21μg/g, primarily dominating by C29(24.9 ± 3.0%), C31 (15.6 ± 1.5%) , C33 (13.2 ± 1.8%), C27 (10.0 ± 0.8%), and C35 (6.2 ± 0.9%). The relative proportions of short-chain (C15+C17+C19), middle-chain (C21+C23+C25)and long-chain (C27+C29+C31) n-alkanes were 3.4±2.2%, 14.1±2.3%, 82.4±3.5 %, respectively. The predominance of long-chain n-alkanes suggests the major contribution from terrestrial plants origin. The CPI values of 4.78±1.05 supported the n-alkanes in sediment have obvious biogenetics feature. The high TAR value of 35.4±22.4 and Paq of 0.17±0.03 also indicated the major terrestrial plants sources of n-alkanes, not from aquatic or algae and photosynthesis bacteria. Among these terrestrial plant origins, the C31/(C27+C29) ratio of 0.45±0.05 suggested more long-chain n-alkanes from woody plants were delivered to the lake than that from herbaceous plants. Higher total AHCs concentrations (57μg/g and 45μg/g, respectively) and lower CPI values (1.71 and 2.54, respectively) were observed in the sediments in the depths at 21cm and 31cm, suggesting the sudden erosion event with mature terrestrial organic matter’s input, because it have obvious even-carbon n-alkanes. Higher concentrations of short-chain n-alkanes (2.81μg, 2.05μg, respectively) and lower TAR values (6.6 and 9.1, respectively ) were observed in the sediments in the depths at 13cm and 19cm, suggesting the aquatics environment change in these period.

並列關鍵字

Aliphatic Hydrocarbon Compositions ； Lake sediment

參考文獻

李政益(2004)，恆春半島東源谷地3000年來的沉積物孢粉分析，碩士論文，國立台灣大學地質科學研究所，台灣台北

Brincat, D., Yamada, K., Ishiwatari, R., Uemura, H., Naraoka, H., (2000), Molecular-isotopic stratigraphy of long-chain n-alkanes in Lake Baikal Holocene and glacial age sediments, Organic Geochemistry, 31. 287–294

Doskey, Paul V., (2001), Spatial Variation and Chronologies of Alighatic Hydrocarbons in Lake Michigan Sediment. Environmental Science & Technology, 35, 247-254.

Ficken, K. J., B. Li, D. L. Swain, and G. Eglinton (2000), An nalkane proxy for the sedimentary input of submerged/floating freshwater aquatic macrophytes. Organic Geochemistry, 31, 745–749.

Filley, T. R., Freeman, K. H., Hatcher, P. G., Bianchi, T. S., Baskaran, M., Colarusso, L. A. and Hatcher, P. G., (2001), An isotopic biogeochemical assessment of shifts in organic matter input to Holocene sediments from Mud Lake, Florida. Organic Geochemistry, 32, 1152-1167.