本研究主要分析台灣宜蘭縣三星鄉的大湖湖泊底泥中脂肪族碳氫化合物(Aliphatic Hydrocarbons Compositions, AHCs) C14至C35直鏈烷濃度分佈狀況,以生物指標(Biomarker molecule proxies)評估底泥中有機物來源及貢獻量。岩芯深度130.5公分,年代分佈現今到600年前,分析樣品數合計115個。總直鏈烷C14~C35濃度平均為16.1±8.0 μg/g。長碳鏈(C26~C32) 直鏈烷濃度平均為9.1±5.2 μg/g,長碳鏈碳優指數CPIL平均3.8±1.01,顯示長碳鏈奇數碳皆可能源自陸源高等植物。Paq值平均0.25±0.06,顯示600期間大湖皆有水生植物; C31/ (C27+C29)比值平均0.62±0.13,顯示生長於集水區陸生植物可能以木本植物為主,變量不大。短碳鏈直鏈烷(C14~C20) 濃度平均為2.50±1.3 μg/g,短碳鏈直鏈烷佔總直鏈烷濃度19.2%±12.2 %。短碳鏈碳優指數CPIS平均0.74±0.3,顯示大部分樣品具有短碳鏈偶數碳優勢,可能與底泥中為厭氧微生物環境有關。表層兩個樣品(0.25公分, 1.25公分)CPIS分別為1.94及1.55,以奇數碳C17為優勢,可能源自水生浮游藻類沉積。另外,深度7.5 cm~12 cm連續十個樣品 CPIS平均0.12± 0.02遠低於平均值,涵蓋約19年,主要以C14、C16為主,此偶數碳優勢來源是否與底泥微生物環境或源自陸源高等植物將再進一步做探討。
One hundred - fifteen samples from the sediment core were analyzed for aliphatic hydrocarbons (AHCs), C14-C35 n-alkanes, of Dahu Lake, Yilan, Taiwan. The sediment samples were Soxhlet extracted and GC-FID analyzed. The total n-alkanes (C14-C35) concentrations averaged 16.1± 8.0 μg/g. The average concentrations of long chain n-alkanes (C26-C32) and short chain n-alkanes (C14-C20) were 9.11± 5.17 μg/g and 2.50±1.33 μg/g, respectively. The CPI L of 3.79±1.01 indicated biogenetics feature of the major terrestrial plant sources. The CPIS of 0.74± 0.33 (0.10~1.94) also indicated biogenetics feature, including sediment microorganism sources and suspended algae sources. In addition, CPIS values of 10 consecutive samples from 7.5cm to 12cm in depth were 0.12±0.22, resulted from the predominance of C14, C16 and C18. This occurrence of short chain n-alkanes with an even over odd predominance are suggested the source from terrestrial higher plants and need then further to be explored.