Composition and sources of lipid compounds in speleothem calcite from southwestern Oregon and their paleoenvironmental implications
Composition and sources of lipid compounds in speleothem calcite from southwestern Oregon and their paleoenvironmental implications
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DOI：
10.1007/s12665-010-0613-4
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发表时间：
2011-03
影响因子：
2.8
通讯作者：
A. Rushdi;P. Clark;A. Mix;V. Ersek;V. Ersek;B. Simoneit;B. Simoneit;Hai Cheng;R. Edwards
中科院分区：
文献类型：
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作者：
A. Rushdi;P. Clark;A. Mix;V. Ersek;V. Ersek;B. Simoneit;B. Simoneit;Hai Cheng;R. Edwards
我们分析了洞穴方解石从俄勒冈州洞穴国家纪念碑，西南俄勒冈州，以确定保存，分布，浓度和来源的脂肪族脂质化合物保存在方解石。最大的洞穴沉积物生长速率发生在间冰期和最小的冰期。总脂质化合物的浓度范围为0.5至12.9 μg g−1。他们增加的时候，低speleothem的增长速度，这表明稀释，而脂质化合物的表观积累率往往是最高的最快的speleothem的增长速度的时候。这种增加的积累通常对应于温暖的（间冰期）气候的时间，这表明在间冰期期间有更多的有机物质来源和/或在更快速的方解石生长期间更高的化合物捕获效率。脂肪族脂质化合物包括同系物正链烷酸、正链烷醇和正链烷酸甲酯以及甾醇，浓度范围分别为0.3至7.8 μg g g−1、0.4至1.1 μg g g−1、0.5至9.6 μg g− 1和0.1至2.7 μg g g−1。还存在少量的支链正链烷酸甲酯和正链烷二酸二甲酯。高浓度的正链烷酸甲酯是游离脂肪酸在碱性溶液中的酯化反应的结果，所述碱性溶液具有与滴落的洞穴沃茨相关的高pH值。分布格局和地球化学参数和指标表明，主要来源于高等植物的淋溶和微生物残留物来自洞穴系统上方的土壤带。微生物输入的估计百分比范围为总脂质的42%至90%，并且在温暖气候期间也显示出积累的增加。这些保存完好的脂类化合物可作为古环境研究的生物标志物。
We analyzed speleothem calcite from the Oregon Caves National Monument, southwestern Oregon, to determine the preservation, distribution, concentrations and sources of aliphatic lipid compounds preserved in the calcite. Maximum speleothem growth rate occurs during interglaciations and minimum during glacial intervals. Concentrations of the total lipid compounds range from 0.5 to 12.9 μg g−1. They increase at times of low speleothem growth rate, suggesting dilution, whereas the apparent accumulation rate of lipid compounds tends to be highest during times of fastest speleothem growth rate. Such increased accumulation generally corresponds to times of warm (interglacial) climate, suggesting either a greater source of organic materials during interglacial times and/or greater efficiency of compound capture during more rapid calcite growth. Aliphatic lipid compounds include homologousn-alkanoic acids,n-alkanols and methyln-alkanoates and sterols with concentrations ranging from 0.3 to 7.8 μg g−1, 0.4 to 1.1 μg g−1, 0.5 to 9.6 μg g−1and 0.1 to 2.7 μg g−1, respectively. Minor amounts of branched methyln-alkanoates and dimethyln-alkanedioates are also present. The high concentrations of methyln-alkanoates are the result of esterification reactions of free fatty acids in alkaline solutions with high pH values associated with the dripping cave waters. The distribution patterns and geochemical parameters and indices indicate that the major sources of the aliphatic lipids involved leaching from higher plants and microbial residues derived from the soil zone above the cave system. The estimated percentage of microbial inputs ranged from 42 to 90% of the total lipids and also showed an increase in accumulation during warm climates. These well-preserved lipid compounds in speleothem calcite could be used as biomarkers for paleoenvironmental study.