Development of an integrated numerical tool to predict fate and transport of contaminants in groundwater based on a DNAPL migration model wi10008881th entrapment and residual effect of droplets

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The following five major subjects were investigated in this research(1) Study on characteristics of parameters governing the entrapment and residual effect of DNAPL droplets in pores(2) Improvement of prediction accuracy of the DNAPL migration model for contaminant source area in aquifer(3) Identification of the entrapment and residual parameters in contaminated layers(4) Development of a numerical simulation tool based on the DNAPL migration model for both saturated and unsaturated areas(5) Application of the simulation tool with the entrapment and residual parameters to field sites(1) : It was shown that a parameter for residual DNAPL in soil was related to a macroscopic capillary number and a bond number. The following parameters associated with transport, prediction and remediation of contaminants in soils were obtained. 1) Colloid diffusion in water films was a limiting factor in leaching of soil colloids, which enhance the transport of contaminants. 2) Around 50% of the supplied … More colloids were captured in soil. 3) The velocity of colloids was three to four times higher than that of tracer (Br-). 4) The adsorption of pesticides onto colloids was significantly higher (3x10^3 times higher) than that onto soil. 5) For the gas transport in soils, new prediction models for gas transport parameters that consider soil structure such as air content or pore size distribution were developed. These new models enabled to predict the transport of gaseous contaminants in soils.(2) : The fingering model based on Invasion Percolation (IP) theory and the random walk model of the DNAPL liquid drop developed in this study were compared and the prediction accuracy of the DNAPL migration model was improved based on the understanding of characteristic of parameter λ.(3): It was confirmed that the dissolution rate became low even in high velocity condition based on column experiments assuming heterogeneous contaminated soil.(4): The stochastic model represented by Diffusion Limited Aggregation (DLA) or IP theory and the finite difference method for convection dispersion equation were investigated at void, laboratory and field scale, respectively. The stability of difference scheme and the grid dependency of solution and mass-balance were clarified.(5): The application of the developed model to field sites was conducted. From the view point of conservation and utilization of healthy groundwater environment, a framework of the groundwater resource management was established. The problems with the numerical methods and its application to groundwater flow analysis based on small- and large-scale hydraulic models were clarified. Less