The study of reactive transport processes is the basis of characterizing transport behaviors in many disciplines. This dissertation mainly investigates the reactive solute transport problems in two categories: reactive solute transport in fracture-rock matrix system and applications of the coupled depositional-reactive transport of strontium and calcium in the deep-sea carbonate sediments during diagenesis. Concretely, the following scenarios of reactive solute transport in a single fracture are discussed: 1). Many single fractures in the field are filled with sediments, and the transport in such filled single fractures has received much less attention up to present. This study deals with a coupled three-domain transport problem using mobile and immobile domains to characterize a filled single fracture and a matrix domain to characterize the rock. 2). When transport properties are asymmetrically distributed in the adjacent rock matrixes, reactive solute transport needs to be considered as a coupled three-domain problem. Mathematical models are developed for such a problem under the first-type and the third-type boundary conditions to analyze the spatial-temporal concentration and mass distribution in the system 3). Due to the natural heterogeneity of porous media, the fracture dispersivity exhibits to be scale-dependent. This study investigated linear-scale and exponential-scale dependent dispersivities against constant dispersity. The reactive transport modeling is a powerful tool to understand and quantitatively analyze the coupled physical, chemical and biological processes of Earth system. A well-designed model has a better potential to describe the interactions between different processes over large spatial and time scales. This dissertation focuses on the following carbonate diagenesis problems: 1). the model developed in this study estimates the recrystallization and precipitation rates of carbonate sediments and further reconstructs past chemical conditions in the ocean by matching the present measurements of strontium and calcium concentrations in the pore fluids. 2). Mechanical compaction and chemical cementation are responsible for the porosity reduction with depth in carbonate rocks. This coupled model is applied to distinguish the mechanical compaction and chemical compaction and estimate their relative importance on the total porosity reduction. 3). The model is further applied to various sites with different conditions, such as sedimentation rates and carbonate calcite contents. The general relationship between the calcite recrystallization rates and sedimentation conditions will be discussed and summarized.
ETD Chair
Zhan, Hongbin Holder of Endowed Dudley J. Hughes '51 Chair in Geology and Geophysics
