Acid-mine drainage (AMD) is an important source of metals to aquatic ecosystems. Once these metals are input to oxygenated stream water of neutral pH, there may be oxidation of metal ions, precipitation of metal oxyhydroxides, and co-precipitation and/or sorption of metals. Understanding the fate and transport of these metals requires knowledge of the distribution of metals between the suspended solid and dissolved phases. Models exist for the prediction of sorption of metals to oxyhydroxides

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... ases, primarily for hydrous iron oxide (HFO). Visual-MINTEQ now includes a database for a second hydrous oxide phase: hydrous manganese oxide (HMO), which may prove to be an important sorbent for some metals in mining-impacted systems. This paper discusses the comparison between model predicted and observed percentage particulate copper and zinc in stream water collected over a two-year study of the North Fork of Clear Creek, Colorado. It was found that the model over-estimated the percentage of particulate copper actually observed, using HFO as the sole sorbent phase, but that the comparison was within a factor of two. Inclusion of HMO for modeling of the zinc improved the prediction of percentage particulate zinc; however, results indicate that there may be another process controlling particulate zinc in the stream. Additional