Upscaling reactive transport parameters for porous and fractured porous media

A significant challenge in groundwater reactive transport modeling is to develop scale-appropriate parameters to represent physical and chemical heterogeneities that impact solute migration estimates and predictions. This dissertation presents an indicator geostatistics-based upscaling methodology to estimate scale-dependent (temporal and spatial), effective reactive transport parameters (including diffusion coefficient, tortuosity, sorption coefficient, and retardation factor) for porous and fractured porous media with hierarchical reactive mineral facies. The upscaling method provides a theoretical and practical link between controlled experimental results at the laboratory/bench scale to multi-kilometer field scales at which contaminant remediation and risk assessment are conducted. As sorption reactions in porous matrix (or media) are in part determined by mineral properties, a new conceptual model is developed to address the hierarchical structure of reactive mineral facies at the microform, mesoform, and macroform scales.For fractured porous media, the conceptual model of hierarchical reactive mineral facies is integrated with a dual-porosity model to study diffusion of solutes out of fractures and sorption onto the matrix minerals. The effective reactive transport parameters are related to their mean, variance, integral scale and domain size along a pathway through a three-dimensional flow field. The upscaled parameter values increase with the integral scales and are larger than their geometric mean. Simulations conducted with upscaled sorption coefficient and tortuousity are compared very well with high resolution Monte Carlo simulations capturing the parameter spatial variations. Uncertainty analysis of upscaling of theses parameters in fractured porous media shows that when the domain size is very large, the variability of the effective parameters is very small and their mean values of the effective parameters may be directly applied in field-scale transport modeling when the dimensionless domain size is small, the variability of the effective parameters could be very large.For porous media, the conceptual model is used together with the spectral integral method to research transport in uniform hydraulic gradient. The effective reactive transport parameters are related to their mean, variance, integral scale and domain size along a pathway through a three-dimensional flow field. The effective retardation factors approximate their composite arithmetic mean when time and space scales become large enough. The correlation between the hydraulic conductivity and the sorption coefficient can seriously affect the values of the effective retardation factor in temporal and spatial domains.The multi-scale heterogeneities of the media themselves are the source of the scale-dependence of the reactive transport parameters. Results of this study can be extended to explore scale dependence of other important transport parameters in geochemical systems such as rock weathering rate on the earth's surface and mineral-melt distribution coefficients during magma generation in the earth's crust and mantle.