HR: 11:05h
AN: H51G-03    [PDF]
TI: Denitrification in Streams Impacted by Acid Mine Drainage: Effects of Iron, pH, and Potential Electron Donors
AU: * Baeseman, J L
EM: baeseman@colorado.edu
AF: U.S. Geological Survey, 3215 Marine Street, Suite E-127, Boulder, CO 80303 United States
AU: * Baeseman, J L
EM: baeseman@colorado.edu
AF: University of Colorado, Civil Engineering Dept., Boulder, CO 80309 United States
AU: Smith, R L
EM: rlsmith@usgs.gov
AF: U.S. Geological Survey, 3215 Marine Street, Suite E-127, Boulder, CO 80303 United States
AU: Silverstein, J
EM: joann.silverstein@colorado.edu
AF: University of Colorado, Civil Engineering Dept., Boulder, CO 80309 United States
AB: Acid mine drainage (AMD) contaminates between 8,000 and 16,000 km of streams on U.S. Forest Service land in the Western United States and more than 7,000 km of stream in the Eastern U.S. Relatively little is known about nitrogen cycling in these acidic, heavy metal laden streams, however, denitrification can be inhibited under low pH conditions. The objective of this research was to examine AMD sediments for bacteria capable of denitrification. The process of denitrification is known to increase pH, which may be particularly important in acidic environments. Denitrification potential was assessed in AMD sediments from several Colorado AMD impacted streams ranging from pH 2.6 to 4.91, using microcosm incubations with fresh sediments. Added nitrate was immediately reduced to nitrogen gas without any lag period, indicating that denitrification was actively occurring in these environments. Rates varied from 0.33 to 2.52 umoles NO3-N/ g-sediment/ day depending on the site. The pH of the microcosms increased between 0.23 to 1.49 pH units in 5 days, depending on the site. Additional microcosm studies were conducted to examine the effects of iron concentrations (Fe2+ and Fe3+), initial pH conditions, and several potential electron donors. Addition of iron above ambient concentrations seemed to have little effect on denitrification rates, whereas rates increased with increasing initial pH. The addition of carbon and hydrogen stimulated denitrification rates, which in turn increased the rise in pH. These results suggest that not only is denitrification possible in AMD streams, it may also be a useful remediation option, if suitable methods can be found to stimulate activity.
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 4845 Nutrients and nutrient cycling
SC: Hydrology [H]
MN: 2003 Fall Meeting