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

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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.