AWRI Newsletter #59: November 2006

AWRI is currently concluding a 2-year study that was led by Rick Rediske and funded by the U.S. Environmental Protection Agency to analyze the contaminated sediments in Little Black Creek (LBC). Little Black Creek contains some of the highest concentrations of cadmium measured anywhere in the Great Lakes. Because this tributary flows through the city of Muskegon Heights and empties into Mona Lake, which in turn, connects directly to Lake Michigan, we wanted to know the potential ecological and human health impacts associated with these contaminants.

Here, we provide an overview of the metal-sediment transport modeling portion of the study, which was led by AWRI's hydrologic modeler, Xuefeng Chu. Previous studies indicate that Little Black Creek is heavily contaminated by a number of metals and organic chemicals, and the biotic community of the creek has been adversely affected. It is critical to understand where the contaminants, such as cadmium, originate in the system, how they move within the creek, where they accumulate, and how they affect the environment of Mona Lake.

Comprehensive hydrologic and environmental modeling efforts have been made in this project to characterize the LBC watershed, quantify surface runoff and stream flow, estimate soil erosion, and simulate metal (cadmium) and sediment transport in the LBC stream-wetland system. The modeling suggested that the sediment-associated cadmium in the stream bed was the primary source of cadmium contamination in the system. Resuspension and migration of those cadmium-contaminated sediments during storm events could lead to persistent accumulations of cadmium in both Mona Lake and the wetlands adjacent to the creek, which implies a potential threat to the ecosystem. The modeling also indicated that metal and sediment transport in the LBC stream-wetland system is a long-term, slow process under natural conditions. The information from this study will be helpful for evaluating the potential adverse impacts of the sediment-associated cadmium in this ecosystem and for further identifying effective water quality management strategies.

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