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SOLUTIONS APPROXIMATING SOLUTE TRANSPORT IN A LEAKY AQUIFER RECEIVING WASTEWATER INJECTION
Citation:
Chen, C. S. SOLUTIONS APPROXIMATING SOLUTE TRANSPORT IN A LEAKY AQUIFER RECEIVING WASTEWATER INJECTION. WATER RESOURCES RESEARCH 25(1):61-72, (1989).
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Description:
A mathematical model amenable to analytical solution techniques is developed for the investigation of contaminant transport from an injection well into a leaky aquifer system, which comprises a pumped and an unpumped aquifer connected to each other by an aquitard. A steady state groundwater flow field is assumed, where the injected fluids move horizontally in the pumped aquifer and vertically in the aquitard. The unpumped aquifer is assumed to remain in hydrostatic condition due to its large transmissivity. Descriptions of groundwater velocities are based on appropriate leaky aquifer well hydraulics. The model assumes that contaminants are transmitted in the pumped aquifer by radial advection, and in the aquitard by vertical one-dimensional advection and longitudinal dispersion. Two coupled linear differential equations are formulated to deal with this transport problem; they involve variable coefficients dependent on Bessel functions. The unpumped aquifer is incorporated into the model as a boundary condition. Semianalytical transient solutions for concentration distributions in the pumped aquifer and the aquitard can be obtained by numerically inverting the Laplace domain solutions of the model with the Crump [1976] method. However, the steady state solutions of the model are determined in closed forms. In general, the modeling approach neglecting longitudinal dispersion in the pumped aquifer and lateral dispersion in the aquitard does not introduce significant error to the modelling results, as shown by the good agreement between numerical solutions including these two transport mechanisms and the solutions of the proposed model. Within the context of the assumed hydrogeological conditions, the proposed model appears to be a valid approximation to the problem of interest. Type curves for concentration evaluated at the well bore and the top of the aquitard are given, which can be employed to estimate whether the unpumped aquifer would be polluted as the consequence of the injection. Neglecting the leakage effects in a leaky aquifer can cause significant error in studying the transport problem.
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SOLUTIONS APPROXIMATING SOLUTE TRANSPORT IN A LEAKY AQUIFER RECEIVING WASTEWATER INJECTION
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