Linking Redox-Cycling to Hydrogeology: Sedimentological Controls on the Capacity of Aquifers to Reduce Nitrate and other Dissolved Electron Acceptors

将氧化还原循环与水文地质学联系起来：沉积学控制含水层减少硝酸盐和其他溶解电子受体的能力

• 批准号: 497727419
• 负责人: Professor Dr.-Ing. Olaf A. Cirpka
• 金额: --
• 依托单位: Department für Funktionelle und Evolutionäre Ökologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/497727419?language=en
• 关键词: Linking; Redox; Cycling; Hydrogeology; Sedimentological

The physical and chemical make-up of sedimentary aquifers is determined by the geology of the host rock and the local depositional environment at the time of their formation. The latter yields a characteristic constellation of structural elements differing both in grain-size distribution (and thus hydraulic conductivity) and content of redox-active minerals and organic matter. This spatially variable and hierarchically organized distribution controls groundwater flow and solute reactive transport in sedimentary aquifers. The presence of reactive organic or mineral phases determines the potential reactivity for nitrate and other dissolved electron acceptors, but for the reactions to occur the electron bearing sediments must be conduits for flow, that is, that they must have a sufficiently high hydraulic conductivity to allow water borne solutes to reach the reactive solid phases. The dependence on matrix-reactivity is a key reason for sustained nitrate contamination in aquifers, despite denitrification being a high-energy-yielding reaction, and the subsurface harboring the necessary microbial capacity to catalyze it. The proposed project aims at quantitatively linking aquifer hydraulic and biogeochemical properties with the “reactivity” of aquifer sediments, and their ability to reduce nitrate via denitrification. Via a coupled hydrogeological, sedimentological and microbiological field-site investigations, flow-through column experiments with field-collected cores and data-informed reactive transport modelling at the laboratory and aquifer scales, we aim to yield a unique dataset that will enable reliable estimates of site- and facies-specific reactivity estimates to feed larger scale (denitrification) predictive models. The project will rely on Direct-Push field investigations at five sites across a spectrum of hydraulic conductivity, nitrate contamination, and organic matter / redox-active mineral content in Germany and Austria for core-logging and sediment sample extraction. Field surveys will inform biogeochemical flow through experiments that will monitor denitrification and denitrifying microbial activity in sediments. A detailed sedimentological characterization of field collected cores will help elucidate the reactive potential of sedimentological facies and build site-specific conceptual sedimentological models. Reactive transport models will help quantifying reaction-rate coefficients that will ultimately yield estimates of overall sediment reactivity. The latter will feed into aquifer scale virtual floodplain aquifer models based on the concept of “cumulative relative reactivity” to solve for reactive transport. We expect this project to advance our understanding of fundamental sedimentological controls on matrix-mediated redox reactions and microbial activity in aquifers, and yield aquifer-scale models that can predict denitrification as a function of an aquifer’s sedimentological setting.

沉积含水层的物理和化学组成是由主岩的地质情况和形成​​时的当地沉积环境决定的。后者产生了结构元素的特征星座，其粒度分布（以及水力传导率）以及氧化还原活性矿物质和有机物的含量都不同。这种空间可变和分层组织的分布控制着沉积含水层中的地下水流和溶质反应性输送。反应性有机相或矿物相的存在决定了硝酸盐和其他溶解电子受体的潜在反应性，但为了发生反应，带有电子的沉积物必须是流动的管道，也就是说，它们必须具有足够高的水力传导率，以允许水性溶质到达反应性固相。对基质反应性的依赖是含水层持续硝酸盐污染的一个关键原因，尽管反硝化是一种高能反应，并且地下具有催化反硝化所需的微生物能力。拟议项目旨在定量地将含水层水力和生物地球化学特性与含水层沉积物的“反应性”及其通过反硝化减少硝酸盐的能力联系起来。通过水文地质、沉积学和微生物学现场现场调查、现场收集岩心的流通柱实验以及实验室和含水层尺度的数据反馈反应输运模型，我们的目标是产生一个独特的数据集，该数据集将能够可靠地估计现场和相特定的反应性估计，为更大规模（反硝化）预测模型提供支持。该项目将依靠在德国和奥地利的五个地点进行的直推式现场调查，涵盖水力传导率、硝酸盐污染和有机物/氧化还原活性矿物含量，以进行岩心测井和沉积物样品提取。现场调查将通过监测沉积物中反硝化和反硝化微生物活动的实验来了解生物地球化学流。对现场收集的岩心进行详细的沉积学表征将有助于阐明沉积相的反应潜力并建立特定地点的概念沉积学模型。反应输运模型将有助于量化反应速率系数，最终得出总体沉积物反应性的估计。后者将基于“累积相对反应性”概念输入含水层规模的虚拟洪泛区含水层模型，以解决反应性输运问题。我们希望这个项目能够增进我们对含水层中基质介导的氧化还原反应和微生物活动的基本沉积学控制的理解，并产生含水层规模模型，可以预测反硝化作用作为含水层沉积环境的函数。