HR: 09:15h
AN: NB31D-04 INVITED     [Abstracts]
TI: Importance of Stream Denitrification in the Nitrogen Mass Balance of a Midwestern Agricultural Region
AU: * David, M B
EM: mbdavid@uiuc.edu
AF: University of Illinois, Dept. of Natural Resources & Environmental Sciences W503 Turner Hall 1102 S. Goodwin Av., Urbana, IL 61801
AU: Royer, T V
EM: troyer@kent.edu
AF: Kent State University, Dept. of Biological Sciences 256 Cunningham Hall, Kent, OH 44242
AU: Opdyke, M R
EM: opdyke@uiuc.edu
AF: University of Illinois, Dept. of Natural Resources & Environmental Sciences W503 Turner Hall 1102 S. Goodwin Av., Urbana, IL 61801
AU: Tank, J L
EM: tank.1@nd.edu
AF: University of Notre Dame, Dept. of Biological Sciences Galvin Life Sciences Bldg., Notre Dame, ND 46556
AB: Agricultural regions of the Midwestern US have large N fluxes as a result of inputs from fertilizer and biological fixation, and outputs through rivers and grain harvest. These inputs and outputs are not balanced, however, and denitrification has been suggested to be an important loss mechanism. We examined the role of in-stream denitrification in the N mass balance of Illinois, a predominantly agricultural region. Nitrate concentrations in streams were often >10 mg nitrate-N L^-1, suggesting denitrification was not N-limited throughout most of the year. Denitrification rates were measured at many headwater stream sites throughout the year, in both sediments and primary producer habitat, under different geomorphic conditions. Although in-stream denitrification rates were generally high, hydraulic retention time limited the importance of denitrification in terms of export on an annual basis. Geomorphology was important in explaining rates, but extensive channelization has eliminated most in-stream structures, which could have more effectively reduced stream export of N. Therefore, stream denitrification was only minor sink for N and most nitrate in these headwater sites was exported downstream. In the overall mass balance of N, reservoir and in-field denitrification are thought to be much more important than in-stream denitrification.
DE: 1824 Geomorphology (1625)
DE: 1871 Surface water quality
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly