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取决于其形成时的围岩地质和当地沉积环境。后者产生一个特征星座的结构元素不同的粒度分布（从而水力传导性）和含量的氧化还原活性矿物和有机物。这种空间上可变的和有层次的分布控制着沉积含水层中的地下水流动和溶质反应运输。反应性有机相或矿物相的存在决定了硝酸盐和其他溶解的电子受体的潜在反应性，但是为了使反应发生，携带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持续的硝酸盐污染的含水层，尽管反硝化是一个高能量产生的反应，地下窝藏必要的微生物的能力来催化it. The拟议的项目旨在定量连接含水层的水力和生物地球化学性质与含水层沉积物的“反应性”，并通过反硝化减少硝酸盐的能力。通过耦合的水文地质，沉积学和微生物现场调查，流通过柱实验与现场收集的核心和数据知情的反应性运输模型在实验室和含水层规模，我们的目标是产生一个独特的数据集，将使可靠的估计网站和相特定的反应性估计饲料更大规模（反硝化）预测模型。该项目将依靠直推法在德国和奥地利的五个地点进行现场调查，包括水力传导性、硝酸盐污染和有机物/氧化还原活性矿物含量，以进行岩心记录和沉积物样品提取。实地调查将通过监测沉积物中的反硝化和反硝化微生物活动的实验来提供生物地球化学流动的信息。对野外采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性沉积学模型。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值。后者将根据“累积相对反应性”的概念输入含水层规模的虚拟洪泛区含水层模型，以解决反应性运输问题。我们希望这个项目能促进我们对基质介导的氧化还原反应和含水层中微生物活动的基本沉积学控制的理解，并产生含水层尺度模型，可以预测反硝化作用作为含水层沉积学环境的函数。