M7 AM Metals in the Environment: Chemistry and Fate Issues
Monday, 14 November 2005: 8:00 AM - 11:40 AM in 327-329

(BUT-1117-763669) Comparing equilibrium and transport modeling predictions to observed particulate metal transport in a mining-impacted stream (North Fork Clear Creek, CO).

Butler, B¹, Ranville, J¹, Ross, P¹, ¹ Colorado School of Mines, Golden, Colorado, USA

ABSTRACT- 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 co-precipitation 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 Visual-MINTEQ. Another model, WASP4/META4, combines equilibrium speciation with physical transport mechanisms. This paper discusses the predicted particulate copper and zinc using both Visual-MINTEQ and WASP4/META4, as compared to observed particulate copper and zinc during both high- and low-flow spatial sampling events in North Fork Clear Creek. It was found that the dominant processes controlling the fate and transport of metals in the stream include precipitation of iron oxyhydroxides (HFO) and subsequent sorption of the metals to the HFO, and flow conditions. Dissolved organic carbon also appeared to contribute to the fate and transport of copper. 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 creek.

Key words: speciation, HFO, HMO, Visual-MINTEQ