Nitrate removal in stream ecosystems measured by 15N addition experiments: 2. Denitrification

Journal Article · Thu Jan 01 00:00:00 EST 2009 · Limnology and Oceanography

DOI:https://doi.org/10.4319/lo.2009.54.3.0666· OSTI ID:951921

Mulholland, Patrick J ^[1]; Hall, Robert ^[2]; Sobota, Daniel ^[3]; Dodds, Walter ^[4]; Findlay, Stuart ^[5]; Grimm, Nancy ^[6]; Hamilton, Stephen ^[7]; McDowell, William ^[8]; O'Brien, Jon ^[7]; Tank, Jennifer ^[9]; Ashkenas, Linda ^[10]; Cooper, Lee W ^[1]; Dahm, Cliff ^[11]; Gregory, Stanley ^[10]; Johnson, Sherri ^[3]; Meyer, Judy ^[12]; Peterson, Bruce ^[13]; Poole, Geoff ^[14]; Valett, H. Maurice ^[15]; Webster, Jackson ^[15] ; Arango, Clay ^[9]; Beaulieu, Jake ^[9]; Bernot, Melody ^[16]; Burgin, Amy ^[7]; Crenshaw, Chelsea ^[11]; Helton, Ashley ^[12]; Johnson, Laura ^[9]; Niederlehner, Bobbie ^[15]; Potter, Jody ^[17]; Sheibley, Rich ^[6]; Thomas, Suzanne ^[13]

---

1. ORNL
2. University of Wyoming, Laramie
3. Oregon State University
4. Kansas State University
5. Institute of Ecosystem Studies
6. Arizona State University
7. Michigan State University, East Lansing
8. University of Hew Hampshire
9. University of Notre Dame, IN
10. Oregon State University, Corvallis
11. University of New Mexico, Albuquerque
12. University of Georgia, Athens, GA
13. Marine Biological Laboratory
14. Eco-metrics
15. Virginia Polytechnic Institute and State University (Virginia Tech)
16. Murray State University
17. University of New Hampshire

We measured denitrification rates using a field {sup 15}N-NO{sub 3}{sup -} tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban-urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (S{sub Wden}) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N{sub 2} production rates far exceeded N{sub 2}O production rates in all streams. The fraction of total NO{sub 3}{sup -} removal from water due to denitrification ranged from 0.5% to 100% among streams (median of 16%), and was related to NH{sub 4}{sup +} concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling S{sub Wden} were specific discharge (discharge/width) and NO{sub 3}{sup -} concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (U{sub den}) and NO{sub 3}{sup -} concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis-Menten equation. Although U{sub den} increased with increasing NO{sub 3}{sup -} concentration, the efficiency of NO{sub 3}{sup -} removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO{sub 3}{sup -} load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO{sub 3}{sup -} concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO{sub 3}{sup -} concentration.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 951921
• Journal Information: Limnology and Oceanography, Vol. 54, Issue 3; ISSN 0024-3590
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
DENITRIFICATION
ECOSYSTEMS
EFFICIENCY
LAND USE
NITRATES
PRODUCTION
REMOVAL
RESPIRATION
SATURATION
STORAGE
TRANSIENTS
WATER