Modeling Metal and Sediment Transport in a Stream-Wetland System

Abstract

It has been a challenge to couple a stream channel system with adjacent wetlands and to simulate their interactions and the dynamic processes associated with water flow, sediment movement, and contaminant transport. In this study, a physically based model was developed for simulating metal and sediment transport in a coupled stream-wetland system that consisted of the water column, the underlying active bed, and the adjacent wetland subsystems. The model simulated the dynamic interactions and mass exchanges (water, sediment, and metal) between subsystems and accounted for a set of processes related to the two-phase (dissolved and adsorbed phases) metal and sediment transport, including advection, dispersion/diffusion, sorption, settling, resuspension, and sedimentation. The integrated metal-sediment transport model was solved by using a semidiscrete method. Model simulations of cadmium fate and transport were tested against field data from Little Black Creek (LBC) in western Michigan, which was heavily impacted by historic discharges of cadmium originated from metal plating operations. The preliminary modeling results emphasized the important roles of the cadmium-contaminated sediments in cadmium transport in the stream-wetland system (e.g., accumulation in streambed sediments and release through resuspension) and the potential of heavy metal accumulation in Mona Lake, which received discharge from LBC and the adjacent wetlands.