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COMPARING EQUILIBRIUM AND TRANSPORT MODELING PREDICTIONS TO OBSERVED PARTICULATE METAL TRANSPORT IN A MINING-IMPACTED STREAM (NORTH FORK CLEAR CREEK, CO)
Citation:
BUTLER, B. AND J. RANVILLE. COMPARING EQUILIBRIUM AND TRANSPORT MODELING PREDICTIONS TO OBSERVED PARTICULATE METAL TRANSPORT IN A MINING-IMPACTED STREAM (NORTH FORK CLEAR CREEK, CO). Presented at EPA Region 8 , Denver, CO, February 13 - 15, 2007.
Impact/Purpose:
to present information
Description:
Acid-mine drainage (AMD) is an important source of metals to aquatic ecosystems. Once AMD is mixed with oxygenated stream water of neutral pH, there are changes associated with the metals present. These changes include the oxidation of metal ions, precipitation of metal oxyhydroxides, and coprecipitation and/or sorption of metals. Models exist for the prediction of metal speciation in aqueous systems with various processes occurring, such as sorption, precipitation, and physical transport mechanisms. One model that is used to predict the equilibrium speciation of a metal is Visua-MINTEQ; another model, WASP4/META4, combines equilibrium speciation with physical transport mechanisms. This presentation discusses the predicted particulate copper and zinc using both Visual-MINTEQ and WASP4/META4, as compared to observed particulate copper and zinc during both highand low-flow spatial sampling events in North Fork Clear Creek. Processes determined to be necessary in accurate modeling of copper included sorption onto ferric oxyhydroxides (HFO) and complexation with dissolved organic carbon (DOC). Processes determined to be necessary for accurate modeling of zinc included sorption to both HFO and to hydrous manganese oxides (HMO). Visual-MINTEQ more closely represented data during lower flows, while W ASP4/MET A4 more closely represented data during higher flows. Regardless of flow, data indicate there is need for the inclusion of another process in each of the models to accurately represent observed zinc fate and transport.