Colloid‐facilitated groundwater contaminant transport

Abstract

Colloidal particles or dissolved organic matter (DOM) can act as carriers to enhance the transport of contaminants in groundwater by reducing retardation effects. When either of these materials is present, the system can be treated as consisting of three phases: an aqueous phase, a carrier phase, and the stationary solid matrix phase. The contaminant may be present in either or all of these phases. In the work reported, a mathematical model was developed to describe the transport and fate of the contaminant and carrier material in a porous medium. The model is based on mass balance equations describing the transport and fate of the contaminant and carrier in a three‐phase medium. Colloid/contaminant and colloid/matrix mass transfer mechanisms are represented by first‐order kinetics. Equilibrium partitioning of DOM acting as a carrier of the contaminant introduces a significant simplification in the model formulation. For a constant DOM concentration a much smaller retardation coefficient can be obtained in the three‐phase system than the coefficient obtained in a conventional advective/dispersive transport equation for a two‐phase system. The modified retardation coefficient reflects the presence of the mobile carrier by incorporating both the sorption of the contaminant and capture of the carrier on the solid matrix. Numerical solutions for the model were obtained by using a finite difference scheme to provide estimates of contaminant and carrier concentrations. Significant sensitivities to model parameters, particularly the rate constants of carrier capture and sorption were discovered. The numerical results of the DOM carrier effect matched favorably with experimental data reported in the literature.

Review on subsurface colloids and colloid-associated contaminant transport in saturated porous media

“…Most of these studies have assumed equilibrium interactions between the colloidal particles and the contaminant in the dissolved phase [176,189,202,203] and analogous to model developed by Corapcioglu and Jiang [177]. These models predict a reduction of the effective retardation arising out of sorption on to the solid matrix depending on the concentration of the colloidal fines and the partition coefficient for contaminant sorption on the colloidal fines.…”

“…Majority of the studies concerning the development of mathematical models to describe the colloid-facilitated transport of contaminants have been carried out by various researchers during the past ten years [1,2,17,42,137,153,169,176,177,189,202,203]. Most of these studies have assumed equilibrium interactions between the colloidal particles and the contaminant in the dissolved phase [176,189,202,203] and analogous to model developed by Corapcioglu and Jiang [177].…”

“…Corapcioglu and Jiang [177] have proposed, first time the following equilibrium mathematical model to describe the facilitated contaminant transport. This model consists of mass balance equations for fine particles as well as for the contaminants.…”

Model of contaminant transport in porous media in the presence of colloids applied to actinide migration in column experiments

“…The mass balance equations for the colloids can be written as [Corapcioglu and Jiang, 1993] Ot (0Cc) + div (qcCc-0DcVCc)= -Q•'…”

Transport of dissolving colloidal particles in porous media

“…In this study we focus on simulation of contaminant transport involving fly ash colloids with a water-soluble component, such as a heavy metal, by extending the modeling approach developed by Corapcioglu and Jiang [1993]. The focus of our study is the potential effect of colloid dissolution on water quality.…”