Cooperative Ecosystem Studies Unit, Great Rivers CESU

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The USGS Mercury in Stream Ecosystems study team of the National Water-Quality Assessment (NAWQA) Program seeks to provide assistance for the research in the development of computerized contaminant transport models for stream ecosystems. The models will specifically target the complex biogeochemistry of mercury, but certain facets of these models also will be applicable to transport of other contaminants in streams and rivers. This project involves interacting with a team of Federal researchers who develop process-based computer models of watershed hydrology and contaminant transport. The emphasis of this project is to objectively evaluate these models to ascertain which processes, among a large suite of dynamically interdependent processes, govern the transport and chemical speciation of mercury in stream ecosystems. Processes that are coded into complex watershed contaminant transport models such as WASP (Water-quality Analysis and Simulation Program) are broken down into simpler, reduced-form models, and those simpler models are then evaluated to ascertain important model parameters for study watersheds. This process will provide an important tool for selecting parameter values for the more complex contaminant models. Results from this project will improve the capability to model the complex behavior of mercury in stream ecosystems, and may allow better prediction of how ecosystems will respond to changes in mercury inputs, and other ecosystem disturbances that affect watershed hydrology and biogeochemistry. The study will collaborate with current studies of mercury cycling in stream ecosystems in South Carolina and New York. It is anticipated that the modeling tools developed in collaboration with the USGS will be more broadly applicable to ecosystems in other locations.

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