BIO-GEO-CLIM Laboratory, Tomsk State University, Lenina av., 36, Tomsk, Russia.
Geoscience and Environment Toulouse (GET), UMR 5563 CNRS University of Toulouse, 14 Avenue Edouard Belin, 31400 Toulouse, France.
Environ Sci Process Impacts. 2022 Sep 21;24(9):1443-1459. doi: 10.1039/d1em00547b.
The fate of organic carbon (OC), nutrients and metals accumulated in thawing permafrost ice is at the forefront of environmental studies in the Arctic. In contrast to a fairly good understanding of the chemical nature of dissolved OC (DOC) and metals in surface Arctic waters, the speciation and colloidal status of solutes accommodated in the dispersed ground ice remain virtually unknown. Here we used a size fractionation procedure (centrifugal ultrafiltration) to quantify the proportion of colloidal (3 kDa to 0.45 μm) and conventionally dissolved low molecular weight (LMW) fractions of DOC, and major and trace elements in the porewater and ice of 5 peat cores sampled along a 400 km permafrost and climate gradient in the largest peatland in the world, the Western Siberian Lowland (WSL). We discovered that the strong (a factor of 2 to 10) increase in the total dissolved (<0.45 μm) concentration of DOC and most major and trace elements in the peat ice relative to the peat porewater from the thawed layer was essentially linked to an increase in the LMW fraction. This increase in the potentially bioavailable fraction in the peat ice relative to the porewater was especially pronounced for DOC, P and many trace elements including metal micronutrients, and was observed throughout all permafrost zones. This contrasted with element distribution in the upper (thaw) layer, where the majority of these elements were present in the colloidal pool. Following previous experiments on permafrost peatland surface waters, we hypothesized that the freeze-thaw cycles of peat porewater were responsible for generation of the LMW fraction in the bottom part of the peat core. Results of this study demonstrate that carbon, and macro- and micro-nutrients as well as trace metals in ground ice of permafrost peatlands are essentially present in a low molecular weight (<3 kDa) and potentially bioavailable form that can strongly impact the riverine export fluxes of solutes during permafrost thaw.
在北极的环境研究中，处于融化冻土层中的有机碳 (OC)、营养物质和金属的命运是最前沿的问题。与对地表北极水域中溶解 OC (DOC) 和金属的化学性质有相当好的了解相比，溶解在分散的基岩冰中的溶质的形态和胶体状态实际上仍然未知。在这里，我们使用了一种分级分离程序（离心超滤）来定量测定胶体（3 kDa 至 0.45 μm）和传统溶解的低分子量 (LMW) 分数的 DOC 以及主要和微量元素在 5 个泥炭芯的孔隙水和冰中的比例，这些泥炭芯沿世界上最大的西西伯利亚低地 (WSL) 的 400 公里永久冻土和气候梯度进行了采样。我们发现，与解冻层中的泥炭孔隙水相比，泥炭冰中总溶解（<0.45 μm）DOC 和大多数主要和微量元素的浓度（强 2 至 10 倍）的强烈增加基本上与 LMW 分数的增加有关。与孔隙水相比，泥炭冰中潜在生物可利用的分数增加尤其明显DOC、P 和许多微量元素，包括金属微量元素，并且在所有永久冻土带中都观察到了这种情况。这与上层（解冻）层中元素的分布形成对比，其中大部分元素存在于胶体池中。根据对永久冻土泥炭地地表水的先前实验，我们假设泥炭孔隙水的冻融循环是在泥炭芯底部产生 LMW 分数的原因。本研究的结果表明，永久冻土泥炭地基岩冰中的碳以及宏量和微量营养素以及痕量金属基本上以低分子量（<3 kDa）和潜在生物可利用的形式存在，这可能会强烈影响永久冻土融化期间溶质的河流出口通量。
