CAREER:COMBINING LABORATORY EXPERIMENTS, FIELD DATA, AND REACTIVE TRANSPORT MODELING TO QUANTIFY INFLUENCE OF FLUID TRANSPORT ON MINERAL DISSOLUTION RATES ACROSS SCALE

了解自然环境中岩石与水的化学反应速度，可以解开过去气候变化和陆地表面演变的线索，并提高预测地球系统如何应对未来人为扰动的能力。目前，在实验室条件下测量的岩石和水之间的化学反应比在自然系统中测量的水-岩反应要快得多，这使得人们很难真正了解沉积物中岩石破碎的基本地质过程。这个项目将有助于更好地理解水在岩石中流动的方式和岩石溶解的速度之间的联系。这将提高对重要社会问题的认识，如陆地表面对气候变化的响应、地质构造中二氧化碳的封存、环境中污染物的运动和持久性以及非常规油气储层。研究生、高中教师和高中生将聚集在一起，通过研究促进对自然系统中地球化学过程的基本理解。他们将这项研究带到教室，以扩大STEM教育的范围，并为高中生提供体验式学习的机会。在非均质场系统中，数值模拟地球化学过程的能力受到实验室测量和现场测量矿物溶解速率之间2到6个数量级差异的限制。在实验室充分混合的条件下测量的矿物溶解速率不能捕捉到影响现场系统中矿物反应的非均质、不断变化的流体输送的影响。水文性质和流体输送的非均质性是影响矿物溶解速率的众多因素之一。随着长度尺度的增加，流体流动的复杂性和尺度的增加与物理非均质性有关。然而，增加的流动复杂性对矿物溶解速率的影响在很大程度上尚未被探索。为了验证由于物理非均质性引起的流体混合和停留时间变化的增加，输运对矿物溶解速率的控制随尺度而增加的假设，研究者将实验量化孔隙和柱尺度上的矿物溶解速率，并计算野外尺度上的风化速率，以系统地量化流体输运对表观反应速率的影响。复杂的反应输运模型将在所有尺度上使用，以整合数据，并提高我们将实验室推导的反应速率应用于现场尺度系统的能力。提出的工作整合了数据和观测跨尺度与先进的数值方法，以解决低温地球化学的一个重要的未解决的问题：一个尺度的反应速率如何从孔隙到现场尺度？拟建项目的完成将1)提供耦合反应输运的实验数据和直接观测，以验证反应输运过程的数值模拟；2)明确定义水文非均质性影响从孔隙到流域尺度的表观矿物反应速率的条件；3)利用非均质多孔材料的反应输运模拟，推进实验室测量的矿物溶解速率在现场尺度过程中的应用。在大尺度系统中对地球化学过程进行数值模拟的能力对于评估重要的社会问题是必需的，例如气候变化、二氧化碳封存、污染物的命运和运输，以及非常规油气藏的开发和保存。

Understanding how fast rocks chemically react with water in natural environments can unlock clues to past climate change and land surface evolution and advance the ability to predict how Earth systems will respond to future anthropogenic perturbations. Currently, chemical reactions between rock and water measured in laboratory conditions are much faster than water-rock reactions measured in natural systems, making it difficult to truly understand the fundamental geologic process of breaking rock down in sediment. This project will help develop a better understanding of the linkages between the way water moves through rock and how fast rock dissolves. This will enhance knowledge of important societal issues such as land surface response to climate change, sequestration of carbon dioxide (CO2) in geologic formations, movement and persistence of contaminants in the environment, and unconventional hydrocarbon reservoirs. Graduate students, high school teachers, and high school students will come together to advance fundamental understanding of geochemical processes in natural systems through research. They take this research to classrooms to broaden the scope of STEM education and provide experiential learning opportunities for high school students. The ability to numerically simulate geochemical processes in heterogeneous field systems is limited by a two to six order of magnitude difference between laboratory measured and field-scale measured mineral dissolution rates. Mineral dissolution rates measured under well-mixed conditions in the laboratory do not capture the influence of heterogeneous, evolving fluid transport that influences mineral reactions in field systems. Heterogeneity in hydrologic properties and fluid transport is one of the many factors that influence mineral dissolution rates. Increased complexity and scaling of fluid flow related to increasing physical heterogeneity with length scale is well established. However, the influence of increased flow complexity on scaling of mineral dissolution rates is largely unexplored. To test the hypothesis that transport control on mineral dissolution rates increases with scale due to increased fluid mixing and residence time variation induced by physical heterogeneity, the investigator will experimentally quantify mineral dissolution rates at pore and column scale and calculate weathering rates at field scales to systematically quantify the influence of fluid transport on apparent reaction rates. Sophisticated reactive transport models will be employed at all scales to integrate data and advance our ability to apply laboratory derived reaction rates to field scale systems. The proposed work integrates data and observations across scales with advanced numerical methods to address an important unresolved question in low-temperature geochemistry: how does one scale reaction rates from pore to field scales? Completion of the proposed project will 1) provide experimental data and direct observation of coupled reactive transport to validate numerical simulation of reactive transport processes, 2) clearly define conditions where hydrologic heterogeneity impacts apparent mineral reaction rates from pore to watershed scale, and 3) advance application of laboratory-measured mineral dissolution rates to field-scale processes using reactive transport simulation in heterogeneous porous material. The ability to numerically model geochemical processes in large-scale systems is required for the evaluation of important societal issues such as climate change, CO2 sequestration, contaminant fate and transport, and development and preservation of unconventional hydrocarbon reservoirs.