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http://hdl.handle.net/10136/502
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| Title: | Aquifer decontamination by pumping in radial and one dimensional uniform flow fields |
| Authors: | Woodside, Greg D. |
| Issue Date: | 26-Aug-2009 |
| Abstract: | Decontamination of polluted aquifers is an important environmental concern. Pumping from withdrawal wells or french drains to extract dissolved solutes is a possible remediation technique. Two mathematical models for aquifer decontamination using a single withdrawal well with radially converging flow and a french drain with one dimensional flow are developed. In the radial model, the well is taken into account as a mathematical sink located at the center of the plume which is assumed to be radially symmetric. The plume is incorporated into the model as an initial condition capable of representing a wide range of plume geometries. For the one dimensional model, two simple initial conditions of a uniform concentration given by a step function and a sloping straight line are used with a constant dispersion coefficient. Both models assume advection and longitudinal mechanical dispersion as the transport mechanism. Solutions for the one dimensional model are obtained using the Green's function approach and LaPlace transform following the same methodology as Chen and Woodside (1988) used in deriving the solution for the radial model. The radial solution agrees well with the approximate solution of Gelhar and Collins (1971). Using the field data of Pickens and Grisak (1981), the radial model also accurately reproduces the concentration history at the withdrawal well of the single well injection-withdrawal tracer test. When the initial conditions in the two models are formulated with large concentration gradients at the plume boundary, adverse dispersion against the converging groundwater flow causes spreading of solutes beyond the original plume boundary. If the initial conditions gradually decrease to zero concentration at the plume boundary, solutes do not extend beyond the region of original contamination during the withdrawal process. Graphical relationships are developed for estimating the time required to decrease the concentration to 1% of the initial maximum concentration. In general, neglecting dispersion underestimates the total cleanup time. Comparisons between the two models for decontamination efficiency are made using the criteria of decontaminating in equivalent time or withdrawing water at equivalent rates form the single pumping well and the drain. The radial and one dimensional models yield different results over the range of Peclet numbers tested and the use of the correct model is thus important. |
| URI: | http://hdl.handle.net/10136/502 |
| Appears in Collections: | Independent Studies
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| Woodside, Greg D..pdf | | 2089Kb | Adobe PDF | View/Open |
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