MODELING COLLOID AND MICROORGANISM RELEASE WITH TRANSIENTS IN WATER SATURATION AND SOLUTION CHEMISTRY

Colloid and microorganism (particle) release is known to be sensitive to temporal changes in solution chemistry, flow rate, and water content. The conventional first-order detachment model is unable to account for such conditions. This presentation highlights recent advances in simulating particle release with transients in water content and solution chemistry. These models relate particle release to changes in the solid-water and/or air-water interfacial area that contributes to retention. Methods to predict these interfacial areas with transients in solution chemistry, water velocity, and water content are demonstrated. Equilibrium and/or kinetic expressions for particle release with transients are developed and utilized to simulate particle release over a wide range of water saturation and solution chemistry conditions. Results indicate that episodic particle transport is expected in the vadose zone because of transient conditions.