EVALUATION OF HYDROLOGIC PROPERTIES OF POROUS MEDIA BY BREAKTHROUGH CURVE INTERPRETATION

The overall objective of this research was to develop a method for evaluating the homogeneity of the porous media surrounding a potential waste disposal site by breakthrough curve interpretation. This objective was accomplished by (1) developing an experimental solute flow system to correlate breakthrough structure with specific nonhomogeneities present in a media, (2) developing a water solute flow computer simulation model to aid in analysis of experimental curves and evaluate flow under different conditions, and (3) developing a technique to evaluate media flow parameters based on actual breakthrough curves.;A numerical model of the sand column was developed to aid in the analysis of the experimental column runs and to provide guidance in optimizing the experimental time available. A program, PKFIT, was developed to fit each major peak in a breakthrough curve with composite subpeaks to describe the actual flow system as a combination of up to five effective flow paths. General criteria were proposed for using the PKFIT effective parameters to determine the homogeneity of the flow system which generated the breakthrough curves. The homogeneity description obtained from the general criteria showed good agreement with both the experimental curves from this study and in situ breakthrough curves represented in the literature.;The experimental column curves indicate that nonhomogeneous media can cause breakthrough curve structure. The computer model of water flow in known systems supports the experimental findings by showing that the water solute flow path is directly influenced by the different nonhomogeneities present in the media. Thus, the shape and structure of the curve can be correlated with media homogeneity.;The procedure and criteria developed in this research demonstrate that it is possible to evaluate an unknown flow system with respect to the homogeneity and effective hydrologic parameters of the media.;A 0.91-m diameter by 1.52-m in length soil column was constructed. The desired type of nonhomogeneity was introduced into an otherwise homogeneous sand packing in the column. After steady-state flow conditions were established, a tracer spike of radioactive bromine-82 was introduced into the top of the sand. The tracer activity of the column outflow was continuously monitored to obtain the tracer breakthrough curve.