Thermokarst lakes and ponds formed due to thawing of frozen peat in high-latitude lowlands are very dynamic and environmentally important aquatic systems that play a key role in controlling C emission to atmosphere and organic carbon (OC), nutrient, and metal lateral export to rivers and streams. However, despite the importance of thermokarst lakes in assessing biogeochemical functioning of permafrost peatlands in response to climate warming and permafrost thaw, spatial (lake size, permafrost zone) and temporal (seasonal) variations in thermokarst lake hydrochemistry remain very poorly studied. Here, we used unprecedented spatial coverage (isolated, sporadic, discontinuous, and continuous permafrost zone of the western Siberia Lowland) of 67 lakes ranging in size from 102 to 105 m2 for sampling during three main hydrological periods of the year: spring flood, summer baseflow, and autumn time before ice-on. We demonstrate a systematic, all-season decrease in the concentration of dissolved OC (DOC) and an increase in SO4, N-NO3, and some metal (Mn, Co, Cu, Mo, Sr, U, Sb) concentration with an increase in lake surface area, depending on the type of the permafrost zone. These features are interpreted as a combination of (i) OC and organically bound metal leaching from peat at the lake shore, via abrasion and delivery of these compounds by suprapermafrost flow, and (ii) deep groundwater feeding of large lakes (especially visible in the continuous permafrost zone). Analyses of lake water chemical composition across the permafrost gradient allowed a first-order empirical prediction of lake hydrochemical changes in the case of climate warming and permafrost thaw, employing a substituting space for time scenario. The permafrost boundary shift northward may decrease the concentrations and pools of dissolved inorganic carbon (DIC), Li, B, Mg, K, Ca, Sr, Ba, Ni, Cu, As, Rb, Mo, Sr, Y, Zr, rare Earth elements (REEs), Th, and U by a factor of 2–5 in the continuous permafrost zone, but increase the concentrations of CH4, DOC, NH4, Cd, Sb, and Pb by a factor of 2–3. In contrast, the shift of the sporadic to isolated zone may produce a 2–5-fold decrease in CH4, DOC, NH4, Al, P, Ti, Cr, Ni, Ga, Zr, Nb, Cs, REEs, Hf, Th, and U. The exact magnitude of this response will, however, be strongly seasonally dependent, with the largest effects observable during baseflow seasons.

中文翻译：

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多年冻土梯度下西西伯利亚热喀斯特湖泊中碳、养分和金属浓度的空间和季节变化

由于高纬度低地冻结泥炭解冻而形成的热喀斯特湖泊和池塘是非常动态和环境重要的水生系统，在控制向大气排放的碳和有机碳 (OC)、养分和金属向河流的横向出口方面发挥着关键作用和溪流。然而，尽管热岩溶湖泊在评估永久冻土泥炭地的生物地球化学功能以响应气候变暖和永久冻土融化方面很重要，但对热岩溶湖泊水化学的空间（湖泊大小、永久冻土带）和时间（季节性）变化的研究仍然很少。在这里，我们使用了前所未有的空间覆盖范围（西西伯利亚低地的孤立、零星、不连续和连续多年冻土带），在一年中的三个主要水文时期对 67 个大小从 102 到 105 平方米不等的湖泊进行了采样：春季洪水、夏季基流和秋季结冰前的时间。我们展示了溶解 OC (DOC) 浓度的系统性、全季节下降以及 SO4、N-NO3 和一些金属（Mn、Co、Cu、Mo、Sr、U、Sb）浓度的增加在湖表面积，取决于永久冻土带的类型。这些特征被解释为 (i) OC 和从湖岸泥炭中浸出的有机结合金属，通过超冻土流对这些化合物的磨损和输送，以及 (ii) 大型湖泊的深层地下水补给（特别是在连续多年冻土区）。对永久冻土梯度上湖水化学成分的分析允许在气候变暖和永久冻土融化的情况下对湖泊水化学变化进行一阶经验预测，使用空间替代时间场景。永久冻土边界向北移动可能会降低溶解无机碳 (DIC)、Li、B、Mg、K、Ca、Sr、Ba、Ni、Cu、As、Rb、Mo、Sr、Y、Zr、稀有的浓度和库在连续多年冻土带中，地球元素 (REE)、Th 和 U 增加了 2-5 倍，但 CH4、DOC、NH4、Cd、Sb 和 Pb 的浓度增加了 2-3 倍。相比之下，零星区域向孤立区域的转移可能会使 CH4、DOC、NH4、Al、P、Ti、Cr、Ni、Ga、Zr、Nb、Cs、REE、Hf、Th 减少 2-5 倍和 U。然而，这种响应的确切幅度将强烈依赖于季节，在基流季节可观察到最大的影响。K、Ca、Sr、Ba、Ni、Cu、As、Rb、Mo、Sr、Y、Zr、稀土元素 (REE)、Th 和 U 在连续多年冻土带中增加 2-5 倍，但增加CH4、DOC、NH4、Cd、Sb 和 Pb 的浓度增加 2-3 倍。相比之下，零星区域向孤立区域的转移可能会使 CH4、DOC、NH4、Al、P、Ti、Cr、Ni、Ga、Zr、Nb、Cs、REE、Hf、Th 减少 2-5 倍和 U。然而，这种响应的确切幅度将强烈依赖于季节，在基流季节可观察到最大的影响。K、Ca、Sr、Ba、Ni、Cu、As、Rb、Mo、Sr、Y、Zr、稀土元素 (REE)、Th 和 U 在连续多年冻土带中增加 2-5 倍，但增加CH4、DOC、NH4、Cd、Sb 和 Pb 的浓度增加 2-3 倍。相比之下，零星区域向孤立区域的转移可能会使 CH4、DOC、NH4、Al、P、Ti、Cr、Ni、Ga、Zr、Nb、Cs、REE、Hf、Th 减少 2-5 倍和 U。然而，这种响应的确切幅度将强烈依赖于季节，在基流季节可观察到最大的影响。