Using distributions and stable isotopes of n-alkanes to disentangle organic matter contributions to sediments of Laguna Potrok Aike, Argentina
Using distributions and stable isotopes of n-alkanes to disentangle organic matter contributions to sediments of Laguna Potrok Aike, Argentina
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DOI：
10.1016/j.orggeochem.2016.10.001
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发表时间：
2016-12-01
影响因子：
3
通讯作者：
Schefuss, Enno
中科院分区：
文献类型：
--
作者：
Hockun, Katja;Mollenhauer, Gesine;Schefuss, Enno
当使用生物标志物如正构烷烃作为古环境重建的工具时，必须确定其在每个环境中的具体来源。为了实现这一目标，我们分析了一组各种潜在的有机物（OM）的来源，如水生和陆生植物，灰尘，土壤从拉古纳Potrok艾克（LPA）和周边地区在巴塔哥尼亚南部。我们确定了链长分布和氢（三角洲D）和碳（三角洲C-13）同位素组成的正构烷烃的不同OM来源，以量化其相对贡献湖泊沉积物。我们的研究结果表明，中链正构烷烃，n-C-23，主要是由沉水植物产生的，而长链正构烷烃（n-C-29-n-C-31）来自各种陆地来源。我们使用两种方法估计了它们对沉积物的相对贡献，即，基于正烷烃分布及其Δ D和Δ C-13值。这两种方法导致类似的估计水生和陆生的贡献中，长链烷烃的沉积物。62 - 73%的中链n-C-23烷烃来源于水生物，66 - 77%的长链正构烷烃来源于灰尘，14 - 30%来自陆生植物。我们的研究表明，中链正构烷烃，如LPA中的n-C-23烷烃主要来自水生植物，因此有可能记录湖水同位素组成的变化。相比之下，n-C-29烷烃反映了巴塔哥尼亚南部各种陆地来源的同位素信号。(C)2016爱思唯尔有限公司版权所有
When using biomarkers such as n-alkanes as tools for paleo-environmental reconstructions, it is imperative to determine their specific sources for each setting. Toward that goal, we analyzed a set of various potential organic matter (OM) sources such as aquatic and terrestrial plants, dust, and soils from Laguna Potrok Aike (LPA) and surrounding areas in southern Patagonia. We determined chain length distributions and hydrogen (delta D) and carbon (delta C-13) isotopic compositions of n-alkanes of different OM sources in order to quantify their relative contributions to lake sediments. Our results reveal that the midchain n-alkane, n-C-23, is predominantly produced by submerged aquatic plants, whereas long-chain n-alkanes (n-C-29-n-C-31) are derived from various terrestrial sources. We estimated their relative contributions to the sediment using two approaches, i.e., based on the n-alkane distributions and their delta D and delta C-13 values. Both approaches result in similar estimates of aquatic and terrestrial contributions for mid- and long-chain n-alkanes to the sediment. 62-73% of the mid-chain n-C-23 alkanes originate from aquatic sources while 66-77% of the long-chain n-alkanes originate from dust and 14-30% from terrestrial plants. Our study shows that mid-chain n-alkanes such as the n-C-23 alkane in LPA are derived mainly from aquatic macrophytes and thus have the potential to record changes in lake-water isotopic composition. In contrast, the n-C-29 alkane reflects the isotopic signal of various terrestrial sources from southern Patagonia. (C) 2016 Elsevier Ltd. All rights reserved.