Back diffusion + Plume persistence

PhD students Changmin Kim and Seonggan Jang studied solute transport in aquitards, a critical factor for groundwater contaminant remediation and also more broadly solute exchange between subsurface layers encountered throughout geosciences disciplines. Other specific applications include landfill liners and nuclear waste repositories. 

We developed analytical solutions for solving finite domain problems, the solutions were validated with new laboratory experimental data, and the solutions were further applied to diffusion data that spans a large range of scales, both length (cm to m) and temporal (days to millions of years).  

This work demonstrates how measured field data can be used to help understand and manage contaminated sites. The issue of back diffusion is of significant current interest at contaminated aquifer sites (see left). Field-measured data (aquitard concentration profiles) can provide characteristic signatures of plume life cycle stage. 

Based on the shapes of concentration profiles in the aquitard, we can describe the timing of the transitions between aquifer source zone dissolution, dissolution combined with back diffusion from an aquitard, and back diffusion alone. This work supports assessment of plume persistence and human exposure risk. Furthermore, this study addresses proper timing of site management actions in relation to both aquifers and aquitards. 

URANIUM RHIZOFILTRATION

Phytoremediation is an economical and eco-friendly remediation method that can simultaneously restore and protect ecosystems. Among the phytoremediation techniques, rhizofiltration is a method based on which heavy metals or radionuclides are adsorbed from the groundwater by the roots of plants . The mechanisms by contaminant accumulation in plant cell are as follows: extracellular precipitation, cell wall precipitation and adsorption, and adsorption within cells by cytoplasmic compartments or vacuoles. Additionally, most cell walls or epidermal layers of plants are negatively charged and can adsorb cations from groundwater for effective remediation. 

Mananese (Mn)