Characterization and Simulation of the Effects of Redox Zones on the Fate and Transport of Contaminants in the Saturated Subsurface

9506467 Loague人为污染会形成不同氧化还原电位的地球化学带，从而导致许多有害污染物在含水层的不同带中以不同的氧化态存在。这些污染物在不同氧化态下的迁移率可能会有数量级的变化。这使预测地下水污染物的运输、命运和影响的任务变得非常复杂。这里提出的工作将提供深入了解危险化学品在饱和地下的命运和运输。这项工作将建立一个基于物理和化学的模拟协议，这将使未来的工作者能够定量地估计污染物的命运和运输，这些污染物可以在多种氧化状态下退出。位于马萨诸塞州科德角的美国地质勘探局有毒物质水文研究项目现场将作为模型开发和测试的独特数据集。这项工作的预期结果包括i)在科德角现场观察到的负责铁（II）分布的反应的表征以及II)在当前和未来的管理策略下铁和缺氧区的潜在命运。本研究中用于科德角地点的测量和模型方法将作为未来类似污染地点调查的替代方法。拟议的工作将采取的办法分为三个阶段。第一阶段将通过i)开发一套基于热力学的化学反应来控制铁的浓度，ii)分析批量模拟对反应物和产物的浓度和丰度的敏感性来完成。第二阶段将通过研究在科德角站点运输过程中哪些过程会影响铁（II）来完成：i)构建一维模型来模拟污水羽流和铁带的发展；II)考虑限速反应的重要性和影响。在第三阶段，将化学批模型和一维输运模型相结合，开发出科德角油田地下水流、化学形态和溶质输运耦合模型。第三阶段将通过i)建立二维垂直断面地下水流动模型，ii)建立二维垂直断面地下水溶质运移模型，以及iii)耦合流体流动和溶质运移模型来完成。这些模拟将与现场数据进行比较，以评估耦合建模方法的概念发展和预测能力方面的模型性能。

9506467 Loague Anthropogenic contamination can create geochemical zones of different redox potential, which in turn will cause many hazardous contaminants to exist in different oxidation states in different zone of aquifers. The mobilities of these contaminants in the different oxidation states may vary by orders of magnitude. This greatly complicates the task of predicting the transport, fate and effects of groundwater contaminants. The work proposed here will provide insight into the fate and transport of hazardous chemicals in the saturated subsurface. This work will establish a physics and chemistry based simulation protocol that will enable future workers to quantitatively estimate the fate and transport of contaminants that can exit in multiple oxidation states. The well-studied USGS Toxic Substances Hydrology Research Program field site on Cape Cod, MA will serve as a unique data set for model development and testing. The results anticipated from this work include i) characterization of the reactions responsible for the distribution of Fe (II) observed at the Cape Cod site and ii) the potential fate of the iron and anoxic zone under current and future management strategies. The measure and model approach used for the cape Cod site in this study will serve as a surrogate for future investigations at similar contaminations sites. The approach to be taken for the proposed work consists of three phases. The first phase will be accomplished by i) developing a set of chemical reactions, based upon thermodynamics, that control the concentration of iron, and ii) analyzing the sensitivity of batch simulations to concentrations and abundances of reactants and products. The second phase will be accomplished by investigating what processes affect Fe (II) during transport at the Cape Cod site by i) constructing a one-dimensional model to simulate the development of the sewage plume and iron zone and ii) considering the importance and impact of rate-limited reactions. In third p hase the chemical batch modeling and the one-dimensional transport modeling will be integrated to develop a model of coupled groundwater flow, chemical speciation, and solute transport at the Cape Cod field site. The third phase will be accomplished by i) developing a two-dimensional vertical cross-sectional groundwater flow model, ii) developing a two-dimensional vertical corss-sectional groundwater solute transport model, and iii) coupling the fluid flow and solute transport models. These simulations will be compared with field data to evaluate model performance in terms of assessing concept development and predictive capabilities of the coupled modeling approach.