In high latitude environments, silicon is supplied to river waters by both glacial and non-glacial chemical weathering. The signal of these two end-members is often obscured by biological uptake and/or groundwater input in the river catchment. McMurdo Dry Valleys streams in Antarctica have no deep groundwater input, no connectivity between streams and no surface vegetation cover, and thus provide a simplified system for us to constrain the supply of dissolved silicon (DSi) to rivers from chemical weathering in a glacial environment. Here we report dissolved Si concentrations, germanium/silicon ratios (Ge/Si) and silicon isotope compositions (δ³⁰Si_DSi) in Crescent Stream, McMurdo Dry Valleys for samples collected between December and February in the 2014−2015, 2015−2016, and 2016−2017 austral seasons. The δ³⁰Si_DSi compositions and DSi concentrations are higher than values reported in wet-based glacial meltwaters, and form a narrow cluster within the range of values reported for permafrost dominated Arctic Rivers. High δ³⁰Si_DSi compositions, ranging from +0.90‰ to +1.39‰, are attributed to (i) the precipitation of amorphous silica during freezing of waters in isolated pockets of the hyporheic zone in the winter and the release of Si from unfrozen pockets during meltwater-hyporheic zone exchange in the austral summer, and (ii) additional Si isotope fractionation via long-term Si uptake in clay minerals and seasonal Si uptake into diatoms superimposed on this winter-derived isotope signal. There is no relationship between δ³⁰Si_DSi compositions and DSi concentrations with seasonal and daily discharge, showing that stream waters contain DSi that is in equilibrium with the formation of secondary Si minerals in the hyporheic zone. We show that δ³⁰Si_DSi compositions can be used as tracers of silicate weathering in the hyporheic zone and possible tracers of freeze-thaw conditions in the hyporheic zone. This is important in the context of the ongoing warming in McMurdo Dry Valleys and the supply of more meltwaters to the hyporheic zone of McMurdo Dry Valley streams.

在高纬度环境中，冰川和非冰川化学风化都会向河水供应硅。这两个末端成员的信号通常被河流集水区的生物吸收和/或地下水输入所掩盖。南极的麦克默多干谷溪流没有深层地下水输入，溪流之间没有连通性，也没有地表植被覆盖，因此为我们提供了一个简化的系统，以限制冰川环境中化学风化对河流的溶解硅（DSi）的供应。这里，我们报告固溶Si浓度，锗/硅比（锗/ Si）和硅同位素组成（δ ³⁰的Si_的DSi）在新月溪，麦克默多干旱谷采集2014年至2015年，2015年至2016年和2016年至2017年澳大利亚南方季节的12月至2月之间的样本。的δ ³⁰的Si _DSi的组合物和DSI浓度比的值报道的高基于湿冰meltwaters，并且形成的值的范围内的窄的群集报道了多年冻土为主北极河流。高δ ³⁰硅_DSI公司组成范围从+ 0.90‰到+ 1.39‰，这归因于（i）冬季低渗区孤立袋中水冻结期间无定形二氧化硅的沉淀，以及融水-高渗区中未冻结袋中Si的释放。在夏季的夏季进行交换，以及（ii）通过长期吸收粘土矿物中的Si和季节性吸收Si来增加Si同位素分馏，这些Si叠加在这个冬季衍生的同位素信号上。有δ没有关系³⁰的Si _DSi的季节性和每天的放电组合物和DSI浓度，显示出流水含有DSi的是处于平衡的潜流带形成次级硅的矿物质。我们表明，δ ³⁰硅_DSI公司该组合物可以用作示踪剂区域中硅酸盐风化的示踪剂，以及示踪剂区域中冻融条件的可能示踪剂。这在麦克默多干旱谷持续升温和向麦克默多干旱谷流失带供应更多融化水的背景下非常重要。