HR: 13:30h
AN: NB23E-01    [Abstracts]
TI: Linking Denitrification to Channel Geomorphology in Agricultural Streams
AU: * Opdyke, M R
EM: opdyke@uiuc.edu
AF: Department of Natural Resources and Environmental Science, University of Illinois, Urbana, IL 61801 United States
AU: David, M B
EM: mbdavid@uiuc.edu
AF: Department of Natural Resources and Environmental Science, University of Illinois, Urbana, IL 61801 United States
AU: Rhoads, B L
EM: brhoads@uiuc.edu
AF: Department of Geography, University of Illinois, Urbana, IL 61801 United States
AB: Agricultural streams in east-central Illinois have elevated nitrate concentrations (10 to 20 mg N L^-1) contributing to greater denitrification rates in sediments. However, reduced retention times and extensive stream channelization limit the effectiveness of denitrification as a removal mechanism for water column nitrate. In this study, we compared geomorphic controls of denitrification in six channel reaches varying in geomorphology, organic matter, and nitrate concentration. Denitrification rates were measured monthly between June 2003 and February 2005 using the acetylene inhibition procedure (chloramphenicol was added to control for denitrifier growth). We found in meandering and channelized reaches of greater nitrate concentrations and fine substrate, denitrification rates averaged 19 mg N m^-2 h^-1. In areas of lesser nitrate concentrations and coarse substrates, denitrification rates were comparably lower at 3.0 mg N m^-2 h^-1 in meandering reaches and 0.80 mg N m^-2 h^-1 in channelized reaches. Our study concluded that denitrification rates were strongly linked to geomorphic variability, organic matter, substrate composition, and nitrate concentration. A strong geomorphic connection appeared with substrate composition showing that greater nitrogen removal in channel conditions of fine substrate are more effective.
DE: 1806 Chemistry of fresh water
DE: 1824 Geomorphology (1625)
DE: 1845 Limnology
DE: 9902 NABS Student Award Applied Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly