A field study of non-reactive transport behavior and evaluation of diffusion mediated processes

Abstract

Two multi well, forced-gradient, tracer tests were performed at the Little Creek Naval Amphibious Base, Virginia Beach, Virginia as part of a field groundwater remediation demonstration. Breakthrough of bromide, deuterium and fluorescein was monitored at three extraction wells. A multi-tracer technique can elucidate upon the effects of diffusion and dispersion at the field-scale. Solute transport behavior was evaluated using breakthrough curves from extraction wells E2, E3, and E6 as well as with finite-difference flow and transport models. For the pre and post tracer tests, the magnitude of the dispersion and dispersivity coefficients were different for deuterium, bromide, and fluorescein. This indicates that diffusive mass transfer may influence the tracers, possibly as a result of diffusion between the sandy and more silty clay units at the site. These results demonstrate the effectiveness of using a multi-tracer test method to examine the processes that affect solute transport such as diffusion-mediated mass transfer processes.