Dynamics of re-mobilization of colloidal particles in soils by physico-chemical disturbances

Transport of colloidal particle contaminants in environmental porous media is of significant interest because soils are the primary filter for water resources. Traditionally, soils are managed as efficient filters that permanently remove particles from infiltrating groundwater or landfill leachate. Nevertheless, disturbances in flow hydrodynamics and chemistry are known to significantly remobilize particles in porous media. Common examples of events that trigger such physico-chemical disturbances include intermittent well-pumping episodes and rain/irrigation infiltration events, which are seldom managed.

This project investigates the dynamics of colloidal particle remobilization through laboratory experiments. Here, the behavior of numerous individual particles is tracked as they move, deposit, and subsequently become remobilized in a porous medium. The novelty of the approach is in the combined use of a transparent soil-surrogate that permits full optical access to the pore space with a three-dimensional particle tracking system. Data on the position of particles in time and space are subsequently used to directly quantify the kinetics of particle attachment/detachment processes in relation to the magnitude and type of disturbance imposed. The primary objective of the work is to identify the sets of conditions that increase the susceptibility of soils to quickly release particle contaminants to flowing groundwater. Ultimately, this information can be used to design land management strategies that prevent the occurrence of such high risk conditions, thereby safeguarding groundwater quality.