Photochemical Processes Controlling Manganese Chemistry in Pristine and Contaminated Mountain Streams

EPA Grant Number: R826649
Title: Photochemical Processes Controlling Manganese Chemistry in Pristine and Contaminated Mountain Streams
Investigators: McKnight, Diane M. , Hrncir, Duane
Institution: University of Colorado at Boulder , The University of Texas at Dallas
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 1998 through September 30, 2001
Project Amount: $351,175
RFA: Exploratory Research - Environmental Chemistry (1998) RFA Text |  Recipients Lists
Research Category: Sustainability , Land and Waste Management , Air , Engineering and Environmental Chemistry

Description:

Mountain streams receiving acid mine drainage are typically enriched in Al, Fe, and Mn. For Fe, photochemical reactions control critical aspects of chemical speciation and transport. We hypothesize that Mn photochemistry is also important in controlling Mn speciation and transport. We will characterize diel variations in Mn speciation and quantify rates of photochemical reactions at the stream scale.

Approach:

Our approach is based upon examining two stream scenarios; 1) a neutral pH stream with high dissolved Mn concentrations in which direct Mn photochemical reactions are expected to be most important and 2) an acidic stream with Fe concentrations greater than Mn concentrations in which Mn chemistry may be controlled by cascading Fe photochemical reactions. We will also measure diel Mn variations in a pristine stream. We will employ laboratory experiments to characterize reaction rates with streambed substrates, will measure rates of microbial processes involving Mn and will conduct in-stream perturbation experiments to probe dominant reactions. For the perturbation experiments we will use conservative tracers to quantify the hydrology and will use reactive solute transport codes (OTIS and OTEQ) to interpret the experiments.

Expected Results:

From this research we will determine the dominant photochemical reactions contributing to the transport of Mn and other trace metals in mountain streams receiving acid mine drainage or other sources of excess trace metals. From our field experiments, we will be able to quantify the processes at the stream scale using reactive solute transport codes. This research will provide important tools for understanding and quantitatively modeling trace metal transport in surface waters. Acid mine drainage is a major water quality problem in several major regions of the United States and these modeling tools will be useful in evaluating the change in in-stream water quality from different pollution abatement approaches.

Publications and Presentations:

Publications have been submitted on this project: View all 13 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 3 journal articles for this project

Supplemental Keywords:

water, sediments, chemical transport, metals, restoration, pollution prevention, environmental chemistry, modeling, Rocky Mountains, Colorado, CO, EPA Region 8, Scientific Discipline, Air, Geographic Area, Hydrology, Environmental Chemistry, State, Chemistry, Engineering, Chemistry, & Physics, EPA Region, manganese speciation, fate and transport, mountain streams, acid mine drainage, stream ecosystems, chemical transport modeling, chemical kinetics, Region 8, photochemical processes, heavy metals

Progress and Final Reports:

  • 1999
  • 2000 Progress Report
  • Final Report