Dissolved and colloidal contaminant transport in a partially clogged fracture

Abstract

A water‐saturated fracture, partially clogged with porous material coating the fracture surfaces, is considered. Fluid flow and contaminant transport in this fracture are significantly altered relative to an unclogged fracture. Analytical expressions are developed for the water velocities in the clogged and the unclogged regions in the fracture and the asymptotic longitudinal dispersion coefficient for the system. For highly adsorbing dissolved contaminants or large colloids, the slow diffusion within the porous region causes enhanced dispersion. In a standard tracer test, colloidal contaminants will arrive earlier than dissolved tracers for either one of two reasons: (1) colloids confined to the unclogged portion of the fracture will have a larger average velocity or (2) colloids that can diffuse into the porous region have very low Brownian dififusivities, resulting in a large longitudinal dispersion due to the inverse relationship between Taylor dispersion and Brownian diffusion. The average velocity or asymptotic longitudinal dispersion coefficient can be orders of magnitude greater than that for a molecular tracer.

Deposition of Silver Nanoparticles in Geochemically Heterogeneous Porous Media: Predicting Affinity from Surface Composition Analysis

“…Beyond the engineering scope, the deposition process is also strongly relevant to environment and human health because it determines the transport and fate of colloids in ground water and other aquatic systems. Among these particles some are by themselves environmental contaminants (Kessler and Hunt ;Buddemeier and Hunt 1988) while some serve as vehicles to facilitate the transport of a variety of other contaminants that otherwise would be relatively immobile without the presence of the colloids (McCarthy and Zachara 1989;Corapcioglu and Jiang 1993;Grolimund, Borkovec et al 1996;Ryan and Elimelech 1996). Different types of environmentally relevant particles have been studied, including various minerals, Rajagopalan and Chu 1982;Puls and Powell 1992;Ryde, Kihira et al 1992) bacteria and viruses, (Logan, Hilbert et al 1993;Pieper, Ryan et al 1997;Ryan, Elimelech et al 1999;Redman, Walker et al 2004;Walker, Hill et al 2005) and engineered nanoparticles (Lecoanet, Bottero et al 2004;Brant, Lecoanet et al 2005;Saleh, Phenrat et al 2005;Chen and Elimelech 2006;Espinasse, Hotze et al 2007;Jaisi, Saleh et al 2008).…”

Impact of intermittent rainwater and wastewater flow on coated and uncoated fractures in chalk

“…Kessler and Hunt [1994] suggested that when these materials clog the aperture, their porosity will dominate flow rates through the fractures. The roughness of fracture surfaces may also change over time as a result of mineral weathering [Anbeek 1992a, b; Anbeek et al, 1994; Murphy, 1993].…”

Colloid dispersion in a uniform-aperture fracture

“…In a uniform-aperture fracture, the Taylor dispersion coefficient is only valid under fully developed flow conditions, that is when a fracture exceeds an entrance length defined as [25] (3)…”