摘要
A long-term large-scale variably-saturated subsurface numerical solution of flow and transport are conducted and presented as a simple and fast computational method. Therefore, it is appropriate to develop such a simplified model that focus on the main processes operating at the pertinent time and space scales, based on the error introduced by the simpler model which is acceptable and also was compared to the uncertainties associated with the spatial and temporal variation of boundary conditions. To assess leachate transport as contamination potential it requires calculation of drainage water volume and contamination concentration. A practical, quantitative pollution transfer assessment tool can be developed to enable technical service providers and other practitioners to estimate potential pollution transfer and design best management practices for land waste management pollution systems in order to estimate and control pollution transport to soil and groundwater. The objective of this paper is to describe governing numerical equation and solution algorithm of pollution transport mechanisms and also essential factors which are included in developing relatively simple and practical tools to quantify pollution loss, advection, diffusion and sorption in pollution transport into the groundwater at landfill sites. The paper presents the development of a two-dimensional numerical model that can be used for quantifying groundwater inputs and associated contaminant discharge from a landfill into the affected aquifer. The presented computing results reveal that the proposed model can be used for the simulation of contaminant transport in aquifers in any scale. This numerical solution is established on finite difference, finite-volume solution advection-diffusion linear sorption with first order decay equation. To show the capability of proposed model, the results of a case study are presented in the paper as simulating leachate transport at a 2000 ton/day landfill facility assesses leachate migration away from the landfill in order to control associated environmental impacts, particularly on groundwater wells gradient of the site. Leachate discharge from landfills is the main route for release of the organic and inorganic contaminants through subsurface, commonly encountered in the refuse. Leachate quantity and potential percolation into the subsurface are estimated by the proposed model. A comprehensive sensitivity analysis to leachate transport control parameters was also conducted. Sensitivity analysis suggest that changes in source strength, aquifer hydraulic conductivity, and dispersivity have the most significant impact on model output indicating that these parameters should be carefully selected when similar modeling studies are performed. The sensitivity of the model to variations in input parameters results in two opposing patterns of contaminant concentration. While higher groundwater velocities increase the speed of plume spread it also increases the dilution ratio and hence decrease the concentration.