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揭开过去气候变化和陆地表面演化的线索，并提高预测地球系统将如何应对未来人为干扰的能力。目前，在实验室条件下测得的岩石与水之间的化学反应比在自然系统中测得的水-岩石反应快得多，这使得很难真正了解岩石在沉积物中分解的基本地质过程。这个项目将有助于更好地理解水在岩石中移动的方式与岩石溶解速度之间的联系。这将增进对重要社会问题的了解，如陆地表面对气候变化的反应、二氧化碳(CO2)在地质构造中的封存、污染物在环境中的移动和持久性以及非常规碳氢化合物储藏。研究生、高中教师和高中生将走到一起，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课堂上，以拓宽STEM教育的范围，并为高中生提供体验式学习机会。实验室测量的矿物溶解速率与野外测量的矿物溶解速率之间存在2到6个数量级的差异，这限制了在非均质野外系统中数值模拟地球化学过程的能力。在实验室混合良好的条件下测量的矿物溶解速率没有捕捉到影响现场系统中矿物反应的非均质、不断演变的流体传输的影响。水文性质和流体运移的非均质性是影响矿物溶解速率的众多因素之一。流体流动的复杂性和伸缩性的增加与随长度尺度增加的物理非均质性有关，这是很好的确定的。然而，流动复杂性的增加对矿物溶解速率定标的影响在很大程度上还没有被探索。为了验证由于流体混合增加和物理非均质性引起的停留时间变化，对矿物溶解速率的运移控制随着规模的增加而增加的假设，研究人员将在实验上量化孔隙和柱状尺度的矿物溶解速率，并在野外尺度计算风化速率，以系统地量化流体运移对表观反应速率的影响。将在所有尺度上采用复杂的反应输运模型来整合数据，并提高我们将实验室得出的反应速率应用于现场尺度系统的能力。这项拟议的工作将跨尺度的数据和观测与先进的数值方法相结合，以解决低温地球化学中一个重要的悬而未决的问题：一个尺度的反应速度如何从孔尺度到场尺度？拟议项目的完成将1)提供实验数据和对耦合反应运移的直接观测，以验证反应运移过程的数值模拟；2)明确定义水文非均质性影响从孔隙到分水岭尺度的表观矿物反应速率的条件；3)利用非均质多孔材料中的反应运移模拟，将实验室测量的矿物溶解速率应用于现场规模的过程。评估气候变化、二氧化碳封存、污染物去向和迁移以及非常规油气藏的开发和保存等重要社会问题，需要对大规模系统中的地球化学过程进行数值模拟的能力。

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.