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Transport and Fate of Nitrate in Headwater Agricultural Streams in Illinois
Author(s) -
Royer Todd V.,
Tank Jennifer L.,
David Mark B.
Publication year - 2004
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.1296
Subject(s) - denitrification , streams , nitrate , environmental science , sink (geography) , hydrology (agriculture) , nitrogen , nutrient , environmental chemistry , ecology , chemistry , geology , biology , geography , cartography , organic chemistry , computer science , computer network , geotechnical engineering
Nitrogen inputs to the Gulf of Mexico have increased during recent decades and agricultural regions in the upper Midwest, such as those in Illinois, are a major source of N to the Mississippi River. How strongly denitrification affects the transport of nitrate (NO 3 –N) in Illinois streams has not been directly assessed. We used the nutrient spiraling model to assess the role of in‐stream denitrification in affecting the concentration and downstream transport of NO 3 –N in five headwater streams in agricultural areas of east‐central Illinois. Denitrification in stream sediments was measured approximately monthly from April 2001 through January 2002. Denitrification rates tended to be high (up to 15 mg N m −2 h −1 ), but the concentration of NO 3 –N in the streams was also high (>7 mg N L −1 ). Uptake velocities for NO 3 –N (uptake rate/concentration) were lower than reported for undisturbed streams, indicating that denitrification was not an efficient N sink relative to the concentration of NO 3 –N in the water column. Denitrification uptake lengths (the average distance NO 3 –N travels before being denitrified) were long and indicated that denitrification in the streambed did not affect the transport of NO 3 –N. Loss rates for NO 3 –N in the streams were <5% d −1 except during periods of low discharge and low NO 3 –N concentration, which occurred only in late summer and early autumn. Annually, most NO 3 –N in these headwater sites appeared to be exported to downstream water bodies rather than denitrified, suggesting previous estimates of N losses through in‐stream denitrification may have been overestimated.