BIO-GEO-CLIM Laboratory, Tomsk State University, 634050, Tomsk, Russia.
BIO-GEO-CLIM Laboratory, Tomsk State University, 634050, Tomsk, Russia; Institute of Monitoring of Climatic and Ecological Systems, Siberian Branch of the Russian Academy of Sciences, 634055, Tomsk, Russia.
Environ Res. 2024 Jul 1;252(Pt 4):119115. doi: 10.1016/j.envres.2024.119115. Epub 2024 May 9.
Thermokarst (thaw) lakes of permafrost peatlands are among the most important sentinels of climate change and sizable contributors of greenhouse gas emissions (GHG) in high latitudes. These lakes are humic, often acidic and exhibit fast growing/drainage depending on the local environmental and permafrost thaw. In contrast to good knowledge of the thermokarst lake water hydrochemistry and GHG fluxes, the sediments pore waters remain virtually unknown, despite the fact that these are hot spots of biogeochemical processes including GHG generation. Towards better understating of dissolved organic matter (DOM) quality at the lake water - sediment interface and in the sediments pore waters, here we studied concentration and optical (UV, visual) properties of DOM of 11 thermokarst lakes located in four permafrost zones of Western Siberia Lowland. We found systematic evaluation of DOM concentration, SUVA and various optical parameters along the vertical profile of lake sediments. The lake size and hence, the stage of lake development, had generally weak control on DOM quality. The permafrost zone exhibited clear impact on DOM porewater concentration, optical characteristics, aromaticity and weight average molecular weight (WAMW). The lowest quality of DOM, reflected in highest SUVA and WAMW, corresponding to the dominance of terrestrial sources, was observed at the southern boundary of the permafrost, in the sporadic/discontinuous zone. This suggests active mobilization of organic matter leachates from the interstitial peat and soil porewaters to the lake, presumably via subsurface or suprapermafrost influx. Applying a substitute space for time scenario for future evolution of OM characteristics in thermokarst lake sediments of Western Siberia, we foresee a decrease of DOM quality, molecular weight and potential bioavailability in lakes of continuous permafrost zone, and an increase in these parameters in the sporadic/discontinuous permafrost zone.
多年冻土泥炭地的热喀斯特（融化）湖泊是气候变化最重要的监测器之一，也是高纬度地区温室气体（GHG）排放的重要贡献者。这些湖泊富含有机物，通常呈酸性，并且根据当地的环境和多年冻土融化情况，表现出快速的生长/排水。与热喀斯特湖水中的水文化学和温室气体通量有很好的了解相比，沉积物孔隙水仍然知之甚少，尽管这些是包括温室气体生成在内的生物地球化学过程的热点。为了更好地了解湖泊水-沉积物界面和沉积物孔隙水中溶解有机物质（DOM）的质量，我们在这里研究了位于西西伯利亚低地四个多年冻土带的 11 个热喀斯特湖的 DOM 浓度和光学（UV、可见）特性。我们发现，在沿湖沉积物的垂直剖面中，DOM 浓度、SUVA 和各种光学参数存在系统评估。湖泊的大小，因此，湖泊的发展阶段，对 DOM 质量的控制作用较弱。多年冻土带对 DOM 孔隙水浓度、光学特性、芳香度和重量平均分子量（WAMW）有明显的影响。在多年冻土的南部边界，在零星/不连续带，观察到 DOM 质量最低，反映在最高的 SUVA 和 WAMW 上，这对应于陆地来源的主导地位。这表明有机物质浸出物通过地下或超多年冻土的涌入，从间隙泥炭和土壤孔隙水中积极地迁移到湖中。通过对西西伯利亚热喀斯特湖沉积物中 OM 特征未来演化的替代空间替代时间的情景，我们预计在连续多年冻土带的湖泊中，DOM 质量、分子量和潜在生物利用度将降低，而在零星/不连续多年冻土带的湖泊中，这些参数将增加。
