title: Nitrous oxide emission from denitrification in stream and river networks.
abstract: Nitrous oxide (N(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(2)O via microbial denitrification that converts N to N(2)O and dinitrogen (N(2)). The fraction of denitrified N that escapes as N(2)O rather than N(2) (i.e., the N(2)O yield) is an important determinant of how much N(2)O is produced by river networks, but little is known about the N(2)O yield in flowing waters. Here, we present the results of whole-stream (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(2)O at rates that increase with stream water nitrate (NO(3)(-)) concentrations, but that <1% of denitrified N is converted to N(2)O. Unlike some previous studies, we found no relationship between the N(2)O yield and stream water NO(3)(-). We suggest that increased stream NO(3)(-) loading stimulates denitrification and concomitant N(2)O production, but does not increase the N(2)O yield. In our study, most streams were sources of N(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·y(-1) of anthropogenic N inputs to N(2)O in river networks, equivalent to 10% of the global anthropogenic N(2)O emission rate. This estimate of stream and river N(2)O emissions is three times greater than estimated by the Intergovernmental Panel on Climate Change.
authors.affiliation: Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA. beaulieu.jake@epa.gov
authors.forename: Jake J
authors.initials: JJ
authors.lastname: Beaulieu
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Tank
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Hamilton
authors.forename: Wilfred M
authors.initials: WM
authors.lastname: Wollheim
authors.forename: Robert O
authors.initials: RO
authors.lastname: Hall
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Mulholland
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Peterson
authors.forename: Linda R
authors.initials: LR
authors.lastname: Ashkenas
authors.forename: Lee W
authors.initials: LW
authors.lastname: Cooper
authors.forename: Clifford N
authors.initials: CN
authors.lastname: Dahm
authors.forename: Walter K
authors.initials: WK
authors.lastname: Dodds
authors.forename: Nancy B
authors.initials: NB
authors.lastname: Grimm
authors.forename: Sherri L
authors.initials: SL
authors.lastname: Johnson
authors.forename: William H
authors.initials: WH
authors.lastname: McDowell
authors.forename: Geoffrey C
authors.initials: GC
authors.lastname: Poole
authors.forename: H Maurice
authors.initials: HM
authors.lastname: Valett
authors.forename: Clay P
authors.initials: CP
authors.lastname: Arango
authors.forename: Melody J
authors.initials: MJ
authors.lastname: Bernot
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Burgin
authors.forename: Chelsea L
authors.initials: CL
authors.lastname: Crenshaw
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Helton
authors.forename: Laura T
authors.initials: LT
authors.lastname: Johnson
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: O'Brien
authors.forename: Jody D
authors.initials: JD
authors.lastname: Potter
authors.forename: Richard W
authors.initials: RW
authors.lastname: Sheibley
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Sobota
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Thomas
mesh_terms: D058440:Denitrification / Q000502:physiology*; D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D017752:Greenhouse Effect; D013058:Mass Spectrometry; D008962:Models, Theoretical; D009587:Nitrogen Isotopes / Q000032:analysis; D009609:Nitrous Oxide / Q000378:metabolism*; D045483:Rivers / Q000737:chemistry*; D014481:United States
chemical_list: D009587:Nitrogen Isotopes; D009609:Nitrous Oxide