Distinguishing between old and modern permafrost sources in the northeast Siberian land–shelf system with compound-specific δ 2 H analysis
Distinguishing between old and modern permafrost sources in the northeast Siberian land–shelf system with compound-specific δ 2 H analysis
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通过特定化合物 δ 2 H 分析区分西伯利亚东北部陆架系统的古老和现代永久冻土源
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Ö. Gustafsson
中科院分区：
文献类型：
--
作者：
J. Vonk;T. Tesi;L. Bröder;H. Holmstrand;G. Hugelius;A. Andersson;O. Dudarev;I. Semiletov;Ö. Gustafsson
抽象的。更新世冰川复合体永久冻土沉积物含有大约四分之一储存在永久冻土(PF)地带的有机碳(OC)。当永久冻土融化时，其有机碳被重新动员到(水生)环境中，在那里它可以被降解、运输或埋葬。水生或沿海环境中含有沉积储集层，可以作为过去气候变化的档案。随着整个北极冻土融化的加剧，这些水库是评估可再活化的永久冻土有机碳命运的重要地点。在此，我们对树叶蜡进行了化合物特有的氚(δ2H)分析，以此作为一种工具来区分正在融化的更新世永久冻土(冰复沉积物)和正在融化的全新世永久冻土(来自近地表土壤)释放的有机碳。分析了西伯利亚北极东北部海区δ-PF样品(nδ9)和现代植被和O层(表土-PF)样品(n = 9)中长链正构烷烃(C21~C33)和中长链正构烷酸(C16~C30)的总体地球化学特征(%OC； = 13C；%TN)以及长链正构烷烃(C21~C33)和中长链正构烷酸(C16~C30)的浓度和TN特征。结果表明，这些表层土壤-PF样品具有更高的%OC、更高的OC / TN值和更多的耗竭δ13C-OC值，这表明前者具有更新鲜的土壤和/或植被来源。虽然这两个被调查的来源在总体地球化学水平上有所不同，但在使用叶蜡浓度和比例时，它们实际上是难以区分的。然而，在分子同位素水平上，叶蜡生物标志物δ2H值在表土PF和ICDPF之间存在显著差异。例如，C29正构烷烃的平均δ2H值，表土PF为−246 ± 13 ‰(Mean ± SD)，ICDPF为−280 ± 12 ‰。具有34到50 ‰的动态同位素范围(两个来源之间的差异)；因此，来自叶蜡的单个丰富的生物标记分子的同位素指纹可以作为区分这两个来源的末端成员。我们对拉普特夫海表层沉积物断面进行了分子δ2H示踪剂和另一种来源识别方法--总体有机碳的双碳(δ13C-Δ14C)同位素组成的测试。结果表明，沿着陆架-斜坡断面的总体近海格局相似，但不同方法之间的来源分配不同，这可能突出了两种方法的优势。本研究表明，应用δ-2H叶蜡值可以作为不同冻土区融化有机碳来源和不同归宿的补充定量指标。
Abstract. Pleistocene ice complex permafrost deposits contain roughly a quarter of the organic carbon (OC) stored in permafrost (PF) terrain. When permafrost thaws, its OC is remobilized into the (aquatic) environment where it is available for degradation, transport or burial. Aquatic or coastal environments contain sedimentary reservoirs that can serve as archives of past climatic change. As permafrost thaw is increasing throughout the Arctic, these reservoirs are important locations to assess the fate of remobilized permafrost OC. We here present compound-specific deuterium (δ2H) analysis on leaf waxes as a tool to distinguish between OC released from thawing Pleistocene permafrost (ice complex deposits; ICD) and from thawing Holocene permafrost (from near-surface soils). Bulk geochemistry (%OC; δ13C; %total nitrogen, TN) was analyzed as well as the concentrations and δ2H signatures of long-chain n-alkanes (C21 to C33) and mid- to long-chain n-alkanoic acids (C16 to C30) extracted from both ICD-PF samples (n = 9) and modern vegetation and O-horizon (topsoil-PF) samples (n = 9) from across the northeast Siberian Arctic. Results show that these topsoil-PF samples have higher %OC, higher OC ∕ TN values and more depleted δ13C-OC values than ICD-PF samples, suggesting that these former samples trace a fresher soil and/or vegetation source. Whereas the two investigated sources differ on the bulk geochemical level, they are, however, virtually indistinguishable when using leaf wax concentrations and ratios. However, on the molecular isotope level, leaf wax biomarker δ2H values are statistically different between topsoil PF and ICD PF. For example, the mean δ2H value of C29 n-alkane was −246 ± 13 ‰ (mean ± SD) for topsoil PF and −280 ± 12 ‰ for ICD PF. With a dynamic isotopic range (difference between two sources) of 34 to 50 ‰; the isotopic fingerprints of individual, abundant, biomarker molecules from leaf waxes can thus serve as endmembers to distinguish between these two sources. We tested this molecular δ2H tracer along with another source-distinguishing approach, dual-carbon (δ13C–Δ14C) isotope composition of bulk OC, for a surface sediment transect in the Laptev Sea. Results show that general offshore patterns along the shelf-slope transect are similar, but the source apportionment between the approaches vary, which may highlight the advantages of either. This study indicates that the application of δ2H leaf wax values has potential to serve as a complementary quantitative measure of the source and differential fate of OC thawed out from different permafrost compartments.
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影响因子：
4.3
作者：
T. Opel;S. Wetterich;H. Meyer;A. Dereviagin;M. Fuchs;Lutz Schirrmeister
通讯作者：
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作者：
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通讯作者：
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影响因子：
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作者：
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影响因子：
4.9
作者：
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通讯作者：
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