Modeling the transport of natural organic matter in heterogeneous porous media: Analysis of a field-scale experiment at the Georgetown site, South Carolina
Committee ChairYeh, Jim T.-C.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractObservations that colloidal natural organic matter (NOM) enhances the migration of pollutants in groundwater have focused scientific interest towards the transport of NOM and its adsorptive properties. A small-scale tracer test was performed at a field site in Georgetown, SC, to investigate the movement of NOM under field conditions. Special emphasis was given to the hydrological heterogeneity of the site,with the idea that the flow field must be accurately known in order to distinguish adsorption from the effects of the hydrological processes. 308 slug tests were performed to characterize the spatial variability of hydraulic conductivity at the site. Using the hydraulic conductivity dataset, a three-dimensional transport model successfully reproduced the migration of a chloride plume. In this way, the uncertainties due to hydrological factors were minimized. NOM was then injected in a second tracer test. A two-site adsorption model was used to describe NOM transport. Adsorption on the first site of the model was described by a linear equilibrium isotherm, with adsorption on the second site being described by a linear time-dependent (first order kinetic) reaction. Modeling results indicated that the time-dependent process dominated the adsorption of NOM, with a fast attachment and slow detachment rates. An approximate retardation factor of 77 was estimated for NOM. Because of the high velocities created by the forced gradient, chemical equilibria was not reached during the test. Spatial variability of the chemical properties of the aquifer was identified at two different depths of aquifer. Furthermore, differences at late times between the observed and simulated NOM breakthrough curves suggested possible changes on the adsorption properties of the soil caused by continuous NOM adsorption.
Degree ProgramHydrology and Water Resources