RECOVERY: A contaminated sediment-water interaction model

This paper describes the U.S. Army Corps of Engineers screening-level water quality model (RECOVERY version 3.0) for assessing long-term impacts of co ntaminated bottom sediments on surface waters. The model couples contaminan t interaction between the water column and the bottom sediment, as well as between contaminated and clean bottom sediments. The analysis is intended p rimarily for organic contaminants with the assumption that the overlying wa ter column is well mixed vertically. The contaminant is assumed to follow l inear, reversible, equilibrium sorption and first-order decay kinetics. The system is physically represented as a well-mixed water column (i.e., zero- dimensional) underlain by a vertically-stratified sediment column (i.e., on e-dimensional). The sediment is well-mixed horizontally but segmented verti cally into a well-mixed surface (active) layer and deep sediment. The deep sediment is segmented into variably contaminated and clean sediment regions . Processes incorporated in the model are sorption, decay, volatilization, burial, resuspension, settling, bioturbation, and pore-water diffusion. The solution couples contaminant mass balance in the water column and in the m ixed sediment layer along with diffusion in the deep sediment layers. The m odel was verified against laboratory and field data, as well as against an analytical solution for the water and mixed sediment layers. These comparis ons indicate that the model can be used as an assessment tool for evaluatin g remediation alternatives for contaminated bottom sediments.