Diffusive solute transport and reaction processes in natural and contaminated porous media

天然和污染多孔介质中的扩散溶质传输和反应过程

• 批准号: RGPIN-2017-05540
• 负责人: Al, Tom
• 金额: $ 2.33万
• 依托单位: University of Ottawa
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=711724
• 关键词: Diffusive; solute; transport; reaction; processes

The research program is focused on diffusion and reaction processes in porous media, primarily shallow groundwater systems, with or without anthropogenic contamination. The long-term objective is to improve understanding of coupled diffusion-reaction processes and their controls on solute mobility in groundwater and surface water systems. The proposed research program will address two objectives: 1. In contaminated fractured rock aquifers where natural attenuation of CrVI or chlorinated solvent contamination can be demonstrated, we will build conceptual models by identifying the reactants, products, mechanisms and relative contributions of specific reactions. The conceptual models will be further developed into a numerical framework with the reactive transport code, MIN3P (Mayer et al. 2001). 2. We will improve the understanding of growth mechanisms and time-series variability of chemical and isotopic compositions in growth bands of Fe-Mn nodules that occur at the water-sediment interface in lakes. Knowledge that anthropogenic contaminants in aquifers may undergo natural attenuation by chemical and biological processes integrates well within a risk-based assessment of options for management of contaminated groundwater systems. In cases where it can be shown that natural attenuation mechanisms are active, and risk to human and ecosystem health are low, regulators may decide that aggressive, disruptive and costly remediation approaches are not necessary. We are working with partners in Boeing Corp. and the US EPA to study diffusion and reaction processes that contribute to natural attenuation of Cr(VI) and chlorinated solvents in the matrix pore space of fractured bedrock aquifers. Our contributions include measurement of diffusion transport rates, and the development of geochemical and mineralogical methods to identify mineral reactants and reaction products that allow us to define attenuation reaction processes. Freshwater Fe-Mn nodules have been observed in lakes at the water-sediment interface. The Fe and Mn is thought to be derived from the underlying sediment porewater. In glaciated terrains the nodules are likely as old as the lakes. We will study their origin by conducting detailed studies of the porewater chemistry and stable isotopic composition. Porewater data from the cores will allow for a quantitative study of the upward transport rates for Fe, Mn and trace elements. The nodules, which grow radially similar to tree rings, will be analyzed to determine their age profiles (210Pb, 226Ra, 14C) along the growth direction. This will allow us to define growth rates and total age. These studies will contribute to the understanding of major and trace-element budgets and fluxes to lakes through time. We aim to construct time series for trace-element fluxes at the regional scale that will be valuable in understanding post-industrialization contaminant dispersion.

该研究项目的重点是多孔介质中的扩散和反应过程，主要是浅层地下水系统，有或没有人为污染。 长期目标是提高对耦合扩散反应过程及其对地下水和地表水系统中溶质迁移率的控制的理解。拟议的研究计划将实现两个目标： 1. 在可以证明六价铬或氯化溶剂污染自然衰减的受污染裂隙岩含水层中，我们将通过识别反应物、产物、机制和特定反应的相对贡献来建立概念模型。 概念模型将进一步发展成具有反应性传输代码 MIN3P 的数值框架（Mayer 等人，2001 年）。 2. 我们将提高对湖泊水-沉积物界面铁锰结核生长带中化学和同位素组成的生长机制和时间序列变化的理解。 含水层中的人为污染物可能会因化学和生物过程而自然衰减，这一知识很好地融入了对受污染地下水系统管理方案的基于风险的评估中。如果可以证明自然衰减机制是活跃的，并且对人类和生态系统健康的风险较低，监管机构可能会决定没有必要采取积极的、破坏性的和昂贵的补救方法。我们正在与波音公司和美国环保局的合作伙伴合作，研究有助于裂隙基岩含水层基质孔隙空间中 Cr(VI) 和氯化溶剂自然衰减的扩散和反应过程。我们的贡献包括测量扩散传输速率，以及开发地球化学和矿物学方法来识别矿物反应物和反应产物，从而使我们能够定义衰减反应过程。 在湖泊的水-沉积物界面处观察到淡水铁锰结核。 Fe 和 Mn 被认为来自下面的沉积物孔隙水。 在冰川地带，结核可能和湖泊一样古老。我们将通过对孔隙水化学和稳定同位素组成进行详细研究来研究它们的起源。 来自岩心的孔隙水数据将有助于定量研究铁、锰和微量元素的向上迁移速率。与树木年轮类似的放射状生长的结节将被分析以确定它们沿生长方向的年龄分布（210Pb、226Ra、14C）。这将使我们能够定义增长率和总年龄。这些研究将有助于了解主要元素和微量元素预算以及随时间推移进入湖泊的通量。 我们的目标是构建区域尺度的微量元素通量时间序列，这对于理解后工业化污染物的扩散具有重要意义。