Increasing Arctic temperatures are thawing permafrost soils and liberating ancient organic matter, but the fate of this material remains unclear. Thawing of permafrost releases dissolved organic matter (DOM) into fluvial networks. Unfortunately, tracking this material in Arctic rivers such as the Kolyma River in Siberia has proven challenging due to its high biodegradability. Here, we evaluate late summer abruptly thawed yedoma permafrost dissolved organic carbon (DOC) inputs from Duvannyi Yar. We implemented ultrahigh-resolution mass spectrometry alongside ramped pyrolysis oxidation (RPO) and isotopic analyses. These approaches offer insight into DOM chemical composition and DOC radiocarbon values of thermochemical components for a permafrost thaw stream, the Kolyma River, and their biodegraded counterparts (n = 4). The highly aliphatic molecular formula found in undegraded permafrost DOM contrasted with the comparatively aliphatic-poor formula of Kolyma River DOM, represented by an 8.9% and 2.6% relative abundance, respectively, suggesting minimal inputs of undegraded permafrost DOM in the river. RPO radiocarbon fractions of Kolyma River DOC exhibited no “hidden” aged component indicative of permafrost influence. Thermostability analyses suggested that there was limited biodegraded permafrost DOC in the Kolyma River, in part determined by the formation of high-activation energy (thermally stable) biodegradation components in permafrost DOM that were lacking in the Kolyma River. A mixing model based on thermostability and radiocarbon allowed us to estimate a maximum input of between 0.8% and 7.7% of this Pleistocene-aged permafrost to the Kolyma River DOC. Ultimately, our findings highlight that export of modern terrestrial DOC currently overwhelms any permafrost DOC inputs in the Kolyma River.

中文翻译：

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加速氧化揭示西伯利亚科雷马河中永久冻土溶解有机物的有限存在

北极气温升高正在融化永久冻土并释放古老的有机物质，但这种物质的命运仍不清楚。永久冻土的融化将溶解的有机物 (DOM) 释放到河流网络中。不幸的是，由于其高生物降解性，在北极河流（例如西伯利亚的科雷马河）中追踪这种材料已被证明具有挑战性。在这里，我们评估了来自 Duvannyi Yar 的夏末突然解冻的叶多玛永久冻土溶解有机碳 (DOC) 输入。我们实施了超高分辨率质谱以及加速热解氧化 (RPO) 和同位素分析。这些方法提供了对永久冻土融化流、科雷马河及其生物降解对应物 ( n)热化学成分的 DOM 化学成分和 DOC 放射性碳值的深入了解 = 4）。在未降解的多年冻土 DOM 中发现的高度脂肪族分子式与科雷马河 DOM 中相对缺乏脂肪族的分子式形成对比，分别表示为 8.9% 和 2.6% 的相对丰度，表明河流中未降解的永久冻土 DOM 的输入最少。科雷马河 DOC 的 RPO 放射性碳部分没有表现出表明永久冻土影响的“隐藏”老化成分。热稳定性分析表明，科雷马河中生物降解的永久冻土 DOC 有限，部分原因是在科雷马河中缺乏的永久冻土 DOM 中形成了高活化能（热稳定）生物降解成分。基于热稳定性和放射性碳的混合模型使我们能够估计 0.8% 到 7% 之间的最大输入。7% 的更新世时代永久冻土带至科雷马河 DOC。最终，我们的研究结果强调，现代陆地 DOC 的出口目前超过了科雷马河中任何永久冻土 DOC 的输入。