Graduation date: 1999More efficient methods are needed for the in-situ evaluation of mass transfer\ud parameters which describe the movement of solutes through aquifer material. The\ud objective of this study was to develop a method for estimating diffusion rate and\ud capacity coefficients using a single-well, "push-pull" tracer test. The method consists\ud of the pulse-type injection of a test solution into the saturated zone of an aquifer\ud through the screen of an existing monitoring well. This is followed by a resting\ud (diffusion) period, after which the test solution is extracted from the same well.\ud During the extraction phase a concentration breakthrough curve is obtained. The\ud method uses numerical simulations of the extraction phase breakthrough curve to\ud estimate mass transfer parameters. The methodology was evaluated using a series of\ud laboratory-scale experiments which were performed in a Physical Aquifer Model\ud (PAM). The sediment pack contained in the PAM was modified to create an\ud immobile region governed by diffusive processes.\ud Results from four laboratory-scale experiments are inconclusive in determining the ability of the method to determine mass transfer parameters. Experimental difficulties contributed a significant source of error during the method evaluation. The resting period between the injection and extraction phase was to allow diffusion into the initially solute-free immobile region. Evidence suggests solute was introduced into the immobile region by advective processes during the injection phase of the experiments. Additional experimental work is required to evaluate the methodology. This may include either laboratory or field-scale evaluation of the test method
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