U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings
of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993,
Water-Resources Investigations Report 94-4015
  
Simulation of Reactive Transport During a pH Modification Experiment
in a Mountain Stream Affected by Acid Mine Drainage
by
Robert E. Broshears (U.S. Geological Survey, Lakewood, Colo.),
Briant A. Kimball (U.S. Geological Survey, Salt Lake City, Utah) and Robert
L. Runkel (U.S. Geological Survey, Denver, CO; University of Colorado, Center
for Advanced Decision Support in Water and Environmental Systems (CADSWES))
Abstract
A field experiment in a mountain stream in Colorado has helped to quantify
hydrologic and chemical processes that control the transport of metals in
water affected by acid mine drainage. Injection of sodium carbonate raised
instream pH from 3.5 to a maximum of 5.8. Responses of aluminum and iron
concentrations during the injection indicated the formation of aluminum
and iron hydroxysulfate solid phases. Simulation of these responses using
a reactive transport model reproduced the general aspects of observed patterns
of concentration changes. Discrepancies between simulated and observed concentrations
indicated the importance of chemical interactions between the water column
and the streambed and kinetic restraints on the attainment of equilibrium.
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