Nitrous oxide emission from denitrification in stream and river networks
- University of Notre Dame, IN
- Michigan State University, East Lansing
- University of New Hampshire
- University of Wyoming, Laramie
- ORNL
- Marine Biological Laboratory
- Oregon State University, Corvallis
- University of New Mexico, Albuquerque
- Kansas State University
- Arizona State University
- Oregon State University
- University of Hew Hampshire
- Montana State University
- Virginia Polytechnic Institute and State University (Virginia Tech)
- Ball State University
- University of Georgia, Athens, GA
Nitrous oxide (N{sub 2}O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N{sub 2}O via microbial denitrification that converts N to N{sub 2}O and dinitrogen (N{sub 2}). The fraction of denitrified N that escapes as N{sub 2}O rather than N{sub 2} (i.e., the N{sub 2}O yield) is an important determinant of how much N{sub 2}O is produced by river networks, but little is known about the N{sub 2}O yield in flowing waters. Here, we present the results of whole-stream {sup 15}N-tracer additions conducted in 72 headwater streams draining multiple land-use types across the United States. We found that stream denitrification produces N{sub 2}O at rates that increase with stream water nitrate (NO{sub 3}{sup -}) concentrations, but that <1% of denitrified N is converted to N{sub 2}O. Unlike some previous studies, we found no relationship between the N{sub 2}O yield and stream water NO{sub 3}{sup -}. We suggest that increased stream NO{sub 3}{sup -} loading stimulates denitrification and concomitant N{sub 2}O production, but does not increase the N{sub 2}O yield. In our study, most streams were sources of N{sub 2}O to the atmosphere and the highest emission rates were observed in streams draining urban basins. Using a global river network model, we estimate that microbial N transformations (e.g., denitrification and nitrification) convert at least 0.68 Tg {center_dot} y{sup -1} of anthropogenic N inputs to N{sub 2}O in river networks, equivalent to 10% of the global anthropogenic N{sub 2}O emission rate. This estimate of stream and river N{sub 2}O emissions is three times greater than estimated by the Intergovernmental Panel on Climate Change.
- 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:
- 1005200
- Journal Information:
- Proceedings of the National Academy of Sciences, Vol. 108, Issue 1; ISSN 0027--8424
- Country of Publication:
- United States
- Language:
- English
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