Date of Award

Spring 1-1-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Joseph N. Ryan

Second Advisor

Diane M. McKnight

Third Advisor

Harihar Rajaram

Fourth Advisor

Scott R. Summers

Fifth Advisor

Eric E. Small-Tilton

Abstract

Colloid-facilitated transport of strongly-sorbing contaminants has been observed in the environment under saturated and unsaturated conditions. Our research investigated the role of desorption kinetics on the colloid-facilitated transport of cesium and strontium with respect to: (1) the type of colloids present, (2) moisture content, and (3) the presence of a macropore. A column (13 cm diameter and 33.5 cm long) packed with quartz sand was instrumented with tensiometers and moisture sensors. Solutions with cations and suspensions with cations in equilibrium with colloids were applied with a rainfall simulator. Samples were pumped from the bottom to a fraction collector and measured for pH, colloid concentration, total cation concentration, and dissolved cation concentration.

Our experiments and modeling results demonstrate that slow desorption kinetics of contaminants from the colloids is an important factor in determining whether or not colloid-facilitated transport will be significant. Silica colloids produced very little enhanced transport, while illite clay colloids significantly enhanced transport due to slow desorption kinetics from the frayed edges. Without a macropore present, reducing the moisture content had no effect on enhancing dissolved cesium and strontium transport; however, colloids greatly increased transport rates. A macropore greatly increased the transport rate of dissolved and colloid-associated cesium at higher moisture contents.

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