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Symposium Schedule >
Factors Affecting In-Stream Denitrification Rates in a Nitrogen-Contaminated Stream in the Upper
Illinois River Basin: A Comparison of Two Techniques
L.K. Smith1, R. Antweiler2, J.K. Bohlke3, J. Harvey3,
R.L. Smith2 and M.A.Voytek3
1CIRES, University of Colorado, Boulder, CO
2USGS, Boulder, CO
3USGS, Reston, VA
Denitrification is usually considered one of the most important processes
controlling nitrogen loads in streams and rivers because it has the capability
of permanently removing fixed nitrogen. Elevated loads of nitrogen species are a
common occurrence in rivers draining agricultural watersheds in the Midwestern
United States. Few studies have been conducted in this region to determine the
controls of in-stream nitrogen transformations, such as denitrification and
nitrification, and their net effect on nitrogen transport in small and medium
sized rivers. Current thinking suggests that nitrogen cycling processes should
have the greatest impact in small rivers due to greater contact between river
water and the streambed. The goal of this project is to evaluate the
influence of channel type, hyporheic exchange, microbial community structure,
and water column chemistry on two rivers located in the Upper Illinois River
Basin. Furthermore, two different methods, membrane inlet and isotope ratio
mass spectrometry, are being compared to measure dentirification rates in the laboratory.
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