Isotope Ratio – Discharge Relationships of Solutes Derived From Weathering Reactions
Isotope Ratio – Discharge Relationships of Solutes Derived From Weathering Reactions
复制标题
DOI：
10.2475/001c.84469
复制
发表时间：
2023-08
影响因子：
2.9
通讯作者：
J. Druhan;P. Benettin
中科院分区：
文献类型：
--
作者：
J. Druhan;P. Benettin
迄今为止，绝大多数寻求将流量与溶质浓度联系起来的研究都是基于流域中不随时间变化的流体年龄分布的表示。随着越来越详细的空间和时间数据集可用于风化衍生的河流溶质浓度，将这种质量通量与反应流体通过关键区域环境的瞬态路径联系起来的能力对于定量解释至关重要。流体年龄分布与这些地质溶质的稳定同位素比率之间的关系甚至还不那么发达，但这些特征对于解析产生浓度-排放关系的水-岩石-生命相互作用套件至关重要。在这里，我们首次将具有时变流体年龄分布的水文模型与同位素分馏风化反应的地球化学模型相结合。以SiO2(aq)和相应的硅同位素比δ30Si为例，我们表明风化反应产生的河流溶质的稳定同位素特征反映了流体年龄分布的一个组成部分，该组成部分对于相应的溶质浓度是唯一的。这种独特的敏感性是同位素比与描述给定分水岭的年龄分布参数之间更强联系的结果。这种新颖的建模框架用于为分布在不同气候、地质和生态系统的六个低阶流中的 SiO2(aq) 和 δ30Si 的解释提供定量基础。据我们所知，这是第一个基于过程的正演模型，用于描述流域中随时间变化的排放而产生的风化反应所产生的溶质的同位素特征。
To date, the vast majority of studies seeking to link discharge to solute concentrations have been based on representations of fluid age distributions in watersheds that are time-invariant. As increasingly detailed spatial and temporal datasets become available for weathering-derived riverine solute concentrations, the capacity to link this mass flux to transient routing of reactive fluids through Critical Zone environments is vital to quantitative interpretation. Relationships between fluid age distributions and the stable isotope ratios of these geogenic solutes are even less developed, yet these signatures are vital to parsing the suite of water-rock-life interactions that create concentration-discharge relationships. Here we offer the first merging of a hydrological model featuring time-variant fluid age distributions with a geochemical model for isotopically fractionating weathering reactions. Using SiO2(aq) and the corresponding silicon isotope ratio δ30Si as an example, we show that the stable isotope signatures of riverine solutes produced by weathering reactions reflect a component of the fluid age distribution that is unique to the corresponding solute concentrations. This distinct sensitivity is the result of a stronger link between isotope ratios and the age distribution parameters describing a given watershed. This novel modeling framework is used to provide a quantitative basis for the interpretation of SiO2(aq) and δ30Si in six low-order streams spread across a diversity of climates, geologies, and ecosystems. To our knowledge, this is the first forward and process-based model to describe the isotopic signatures of solutes derived from weathering reactions in watersheds subject to time-varying discharge.