Organic Contaminant Transport Through Clay Liners and Slurry Walls
Richard W. Gullick, Walter J. Weber, Jr., Donald H. Gray, 1996. "Organic Contaminant Transport Through Clay Liners and Slurry Walls", Organic Pollutants in the Environment, James W. Blackburn, Fernando Cadena, Enrique Cazares, S. Chattopadhyay, Richard W. Gullick, Donald Gray, Cliff T. Johnston, Brij L. Sawhney, Samuel Traina, Walter Weber, Brij L. Sawhney
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Chemical waste discharges to landfills and hazardous waste disposal sites must be contained with a high degree of integrity to minimize their potential effects on human health and the environment. Containment practice generally focuses on preventing the escape of leachates, i.e., mobile, soluble portions of the waste. Regulatory requirements typically specify a maximum hydraulic conductivity (typically 10−7 cm/sec) and minimum thickness for landfill barriers, based on the assumption that control of water movement through the barrier will eliminate migration of pollutants. Design criteria are thus generally dominated by considerations of hydraulic conductivity, and typically do not address potential diffusive transport of contaminants (e.g., EPA, 1984). Under sufficiently low permeability conditions in barriers, molecular diffusion may become a dominant transport mechanism. One practical method for minimizing organic contaminant migration by this means is to add sorbent materials, an aspect of barrier design that should be given more attention.
This paper focuses on factors controlling organic contaminant transport through earthen clay barriers, in particular clay liners and soil-bentonite slurry walls. It further addresses the potentially important aspect of diffusive transport through such barriers, and means for preventing or retarding such migration.
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Organic Pollutants in the Environment
Contamination of soils and sediments with organic chemicals and the potential movement of these chemicals to ground water are of increasing public concern. Because of their large surface area and charge, clays comprise the most important inorganic component in controlling the fate and transport of organic chemicals entering soils and sediments. It is essential, therefore, to understand interactions of organic pollutants with clays. The chapters in this volume consider the roles of clays in sorption, transport, attenuation, and bioremediation of organic pollutants in contaminated systems.