Oxidative weathering of sedimentary rocks plays an important role in the global carbon cycle. Rhenium (Re) has been proposed as a tracer of rock organic carbon (OC_petro) oxidation. However, the sources of Re and its mobilization by hydrological processes remain poorly constrained. Here, we examine dissolved Re as a function of water discharge, using samples collected from three alpine catchments that drain sedimentary rocks in Switzerland (Erlenbach and Vogelbach) and Colorado, USA (East River). The Swiss catchments reveal a higher dissolved Re flux in the catchment with higher erosion rates, but have similar [Re]/[Na⁺] and [Re]/[SO₄²⁻] ratios, which indicate a dominance of Re from OC_petro. Despite differences in rock type and hydro-climatic setting, the three catchments have a positive correlation between river water [Re]/[Na⁺] and [Re]/[SO₄²⁻] and water discharge. We propose that this reflects preferential routing of Re from a near-surface, oxidative weathering zone. The observations support the use of Re as a proxy to trace rock-organic carbon oxidation, and suggest it may be a hydrological tracer of vadose zone processes. We apply the Re proxy and estimate CO₂ release by OC_petro oxidation of 5.7 ^+6.6/_−2.0 tC km⁻² yr⁻¹ for the Erlenbach. The overall weathering intensity was ∼40%, meaning that the corresponding export of unweathered OC_petro in river sediments is large, and the findings call for more measurements of OC_petro oxidation in mountains and rivers as they cross floodplains.

中文翻译：

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高山集水区溶解铼的浓度-排放关系揭示其作为氧化风化示踪剂的用途

沉积岩的氧化风化在全球碳循环中起着重要作用。铼 (Re) 已被提议作为岩石有机碳 (OC _petro ) 氧化的示踪剂。然而，Re 的来源及其通过水文过程的动员仍然受到很大限制。在这里，我们使用从瑞士（Erlenbach 和 Vogelbach）和美国科罗拉多州（东河）排放沉积岩的三个高山集水区收集的样本，检查溶解的 Re 作为排水量的函数。瑞士流域显示流域中溶解的 Re 通量较高，侵蚀率较高，但具有相似的 [Re]/[Na ⁺ ] 和 [Re]/[SO ₄ ^2- ] 比率，这表明来自 OC_石油的 Re 占主导地位. 尽管岩石类型和水文气候环境存在差异，但三个流域的河水[Re]/[Na ⁺ ] 和[Re]/[SO ₄ ^2- ] 与水流量之间存在正相关关系。我们认为这反映了 Re 从近地表氧化风化带的优先路由。观察结果支持使用 Re 作为追踪岩石有机碳氧化的替代物，并表明它可能是包气带过程的水文示踪剂。我们应用 Re 代理并估计5.7 ^+6.6 / _-2.0 tC km ^-2  yr ^{-1 的}OC_石油氧化释放的CO ₂对于埃伦巴赫。整体风化强度约为 40%，这意味着河流沉积物中未风化的 OC _petro的相应输出量很大，研究结果要求在穿越洪泛平原时对山河中的 OC _petro氧化进行更多测量。