南极阿德雷岛企鹅粪土沉积物分子地球化学特征

本文分析了南极阿德雷岛Y2湖企鹅粪土沉积层的有机地球化学组成与分布。结果表明企鹅粪土沉积层中正构烷烃以C23为主峰,主要来源于冻土湖沼苔藓植物,样品中高含量的烯烃说明其有机质保存良好。醇类以高浓度的植醇和胆甾烷醇为主,胆甾烷醇和胆甾醇浓度曲线一致,并与企鹅粪土层中的无机元素标型组合的曲线相似,可以作为灵敏的企鹅数量指示剂。酸类组分中以C18饱和脂肪酸为主,在南极低温的环境下,C18∶2酸浓度很低,在很多层次中未检测到,可能是因为Y2沉积物中C18酸以及C18∶2酸主要受企鹅粪影响,而非植被影响。同时在酸性组分中也发现高浓度的胆甾酸。Y2湖中的甾类标志物,甾烯、甾醇、胆甾酸均以C27结构为主,组成单一,低浓度的甾烯和高浓度的甾醇,胆甾酸说明甾类化合物主要受企鹅粪便影响,甾醇和胆甾酸保存良好。综合Y2湖的生物标志物的性质,该沉积物有机质保存良好,主要来源于企鹅粪。

ORGANIC GEOCHEMISTRY OF PENGUIN ORNITHOGENIC SEDIMENT FROM ARDLEY ISLAND,WEST ANTARCTICA

We study molecular geochemical compositions of penguin ornithogenic sediment Y2-1 from Ardley Island,West Antarctica.The results showed that nC_(23) was the main n-alkane,which might derive from tundra mosses.The high concentrations of alkenes in sediments suggested slow diagenesis and good preservation of organic matter in the studied area.At the same time,the concentrations of cholestanol and phytol were high.The concentration profiles of cholestanol and cholesterol were similar to those of the bioelements and could be applied as organic proxies for historic penguin populations.C_(18) alkanoic acid was the main acid in the sediments and the concentrations of unsaturated fatty acids were low and C_(18∶2) acid was trace amount in most samples.This might be explained by that the main organic matter source of the sediment was penguin guano and not vegetation.Bile acid exhibited high concentration in the sediments.However,there were only one C_(27) sterene,C_(27) sterol and one C_(27) bile acid in the sediments,which showed that the input of the steroids was simple.High concentrations of the fecal sterol and bile acid and low concentration of sterene showed good preservation of the sterols and bile acids.In summary,the molecular geochemical compositions of the sediments indicated that the sources of the organic matter were relatively simple,and the organic matter was well preserved there.