Carbon isotopic composition of intact branched GDGT core lipids in Greenland lake sediments and soils
Carbon isotopic composition of intact branched GDGT core lipids in Greenland lake sediments and soils
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DOI：
10.1016/j.orggeochem.2017.04.008
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发表时间：
2017-08-01
影响因子：
3
通讯作者：
Brassell, Simon C.
中科院分区：
文献类型：
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作者：
Colcord, Devon E.;Pearson, Ann;Brassell, Simon C.
支链甘油二烷基甘油四醚（brGDGT）的MBT和CBT指数的基础上使用的代理过去的温度和土壤pH值的变化。虽然这些化合物最初被认为是源于厌氧土壤细菌，现在有令人信服的证据表明，它们也产生在水生环境中。然而，具体的来源微生物仍然未知。我们利用这里的线轴线微燃烧同位素比质谱（SWiM-IRMS）来测量三角洲C-13组成的完整的brGDGT从一系列的湖泊沉积物和土壤，包括样品展示在原位生产的brGDGT。结果表明，三角洲（13）CbrGDGT值和OM在两个湖泊的沉积物序列的下部剖面之间的密切平行。此外，三角洲（13）CbrGDGT值始终比OM的湖泊和周围流域的土壤样品更负。这些值与异养源的混合物和三角洲C-13贫化碳源的优先利用是一致的。个别brGDGT组件的三角洲C-13值确认在原位生产的brGDGT内湖泊dysocompatibility的环境，并建议他们的协会与CH 4水平升高，在夏季可能反映甲烷营养。(C)2017爱思唯尔有限公司版权所有
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are the basis of the MBT and CBT indices used as proxies for past changes in temperature and soil pH. Although these compounds were initially thought to originate solely from anaerobic soil bacteria, there is now convincing evidence that they are also produced within aquatic environments. However, the specific source organism(s) remain unknown. We utilize here spooling wire microcombustion-isotope ratio mass spectrometry (SWiM-IRMS) to measure the delta C-13 composition of intact brGDGTs from a series of lake sediments and soils, including samples exhibiting in situ production of brGDGTs. The results show close parallels between the delta(13)CbrGDGT values and OM in the downcore profiles for sediment sequences from two lakes. In addition, the delta(13)CbrGDGT values were consistently more negative than those of OM for the lakes and soil samples from the surrounding watershed. The values are consistent with a mixture of heterotrophic sources and preferential utilization of delta C-13-depleted carbon sources. The delta C-13 values of individual brGDGT components confirm in situ production of brGDGTs within lacustrine dysoxic environments and suggest that their association with an elevated CH4 level during the summer may reflect methanotrophy. (C) 2017 Elsevier Ltd. All rights reserved.