Collaborative Research: Unraveling Transport in Porous Media through the Integration of Isotopic Tracers, Geophysical Data, and Numerical Modeling

各种估计表明，与美国受污染的地下水场地相关的经济负债高达数千亿美元。这些场所中的每一个都对环境和人类健康构成潜在威胁;近90%的传统法院授权的战略未能充分修复受污染的场所。在许多情况下，这些故障可以归因于补救策略，依赖于经典的概念模型的污染物传输，既不代表地下异质性充分，也不捕捉优先流和低渗透性溶质陷阱。因此，模型在实际问题中的应用仍然存在很大的不确定性。虽然存在许多不同的迁移模型，但了解哪种模型对特定问题“最正确”，对于预测污染物迁移和反应以及场地清理至关重要。该项目将利用污染物迁移、地球物理学、元素和同位素地球化学以及混合驱动反应等领域的方法来满足这一需求。这项研究最终将大大改善补救设计战略，并改善对受污染地下水场所的人类健康风险的评估。 作为这项研究的一部分，新的高中化学实验室将按照科罗拉多高中课程开发，重点是酸碱化学，pH缓冲液和金属地球化学与丹佛公立高中合作。 这些实验室将通过国家地球科学教师协会的“地球科学家”杂志传播到地方发展之外。污染物输送预测的可靠性取决于数值/概念模型对场地地质的适当性。主要问题是：（1）哪些物理上可测量的参数控制溶质质量转移和地球化学反应，（2）哪些参数可以事先预测，（3）哪些数学公式准确地描述了在变化的流速和非均匀性下的特定地点的迁移。现有的溶质运移模型的主要缺陷是模型中控制溶质运移的拟合参数与物理系统之间的联系不好。这项工作的目的是探索控制现有的物理传输模型，特别是那些包括化学反应的预测能力差。扩散引起的元素分馏，扩散引起的锂同位素分馏和地球物理表征将被整合，以探索溶质运移和反应的控制。虽然保守的示踪剂浓度已被用来约束对流分散的传输参数在过去，同位素示踪剂frackets扩散过程中，因此可以提供信息的情况下，扩散主导离子传输的固定孔隙空间。该项目的力量将是增加显着的约束，以控制已知的参数在溶质运移建模，确定其控制的运输过程，并量化的分布在多孔介质中活跃的运输长度尺度和随后的影响反应动力学。产生的实验数据将用于验证水文学界常用的现有理论（即，“本地”与“非本地”运输），并探索新的理论，如有需要，新兴的数据，以发展新的洞察运输和反应行为。

Various estimates suggest that economic liabilities associated with contaminated groundwater sites in the U.S. run into the hundreds of billions of dollars. Each of these sites poses a potential threat to the environment and human health; nearly 90% of the conventional court-mandated strategies fail to remediate polluted sites adequately. In many cases, these failures can be attributed to remediation strategies that rely on classical conceptual models of contaminant transport, which neither represent subsurface heterogeneity sufficiently nor capture preferential flow and low permeability solute traps. As a result, the application of models to practical problems retains significant uncertainty. While many different models for transport exist, understanding which is "most correct" for a given problem is fundamental to the prediction of contaminant transport and reaction and site clean-up. This project will utilize methods from the fields of contaminant transport, geophysics, elemental and isotope geochemistry, and mixing-driven reactions to address this need. The research will ultimately enable significantly improved remediation design strategies and improved assessment of human health risk from contaminated groundwater sites. As part of this research, new high school chemistry labs will be developed following the Colorado high school curriculum focusing on acid-base chemistry, pH buffers, and metal geochemistry in collaboration with a Denver public high school. These labs will be disseminated beyond local development via the National Earth Science Teachers Association's "The Earth Scientist" Journal.The reliability of contaminant transport predictions depends on the appropriateness of the numerical/conceptual model to site geology. The primary questions are: (1) which physically measureable parameters control solute mass transfer and geochemical reactions, (2) which parameters can be predicted a priori, and (3) which mathematical formulations accurately describe site specific transport under varying flow rates and heterogeneity. The main limitation of many existing transport models is the poor connection between fitting parameters governing solute transport in models and the physical system. The objective of the work is to explore controls on the poor predictive ability of existing physical transport models, especially those that include chemical reaction. Diffusion-induced elemental fractionation, diffusion-induced lithium isotopic fractionation, and geophysical characterization will be integrated to explore the controls on solute transport and reaction. While conservative tracer concentrations have been used to constrain advective-dispersive transport parameters in the past, isotopic tracers fractionate during diffusion and can therefore provide information on immobile pore space in cases where diffusion dominates ion transport. The power of this project will be to add significant constraints to the controls of known parameters in solute transport modeling, determine their controls on transport processes, and quantify the distribution of transport length scales active in a porous medium and the subsequent impact on reaction kinetics. The experimental data produced will be used to validate existing theories commonly used by the hydrology community (i.e., "local" versus "non-local" transport), and explore new theories as motivated by emerging data, if needed, to develop new insight into transport and reaction behavior.